Story telling

Storytelling, game mastering or whatever one chooses to call it, is when a roleplayer decides to tell the story that his fellow players will roleplay in. This site will contain a guide to writing "story lines" as well as general information about story telling (ST'ing henceforth).
===What is a Story Line?===
What is a story line? Story lines (SL's henceforth) make up the bulk in longer campaigns/chronicles, but sometimes are played stand alone. They are made up, typically, by scenes, sometimes with "free roaming" play in between scenes.
Chronicles or campaigns are just "longer" SL's, actually made up of many smaller SL's that somehow connect.
===First step: Theme and Setting===
Now, in order to make a SL, you need to figure out a general theme and setting. If the game takes place in our world, what historical period and what country? Locations are important in games that take place in our world, but not so much in fictional worlds, except that you of course still need to describe the setting to the players. The theme can be anything from "war" to "larger scale conflicts" to "horror" or even "everyday dilemmas". Anything really, but it's important to realize what you're gunning for here, even though you intend to cross-theme.
===Step two: Plot concept===
With an idea of your theme and setting written down, proceed to writing a few lines that describes the basic idea of your SL. This is refered to as the plot. Now this is the tricky part, because a plot needs to be liberal enough to allow the players room to assume actions leading to different outcomes, but also needs to stay true to the general idea of the SL. The idea is, that you shape the following steps to match your plot concept, however in certain cases, you might want to do it differently. Just skip this phase and proceed to the next steps, and let the plot shape itself, and thus creating a much more openended story line. When creating your storyline, remember that drama is important. The plot gets boring if nothing exciting happens.
What you're looking for in a plot concept is the essence of a plot. "Princess kidnapped by dragon - Half kingdom and aforementioned princess as wife offered in reward to anyone who secures safe return" is a fairly cliché concept for a plot that doesn't need to be a cliché. You could build a very long and interesting plot around a princess being kidnapped by a dragon. 
"Political schemes for rulership of city" could be an interesting plot concept for a vampire the masquerade game, but might be less interesting if you're playing Dungeons & Dragons. Not saying it couldn't work in D&D either though! 
===Step three: NPC's===
A plot in the essense, is usually when person A wants something, and person B does not want this to happen, or vice versa. If not this exact scenario, it's usually something along these lines. In order for there to be a plot, you need NPC's (not exactly true, but most scenario's have NPC's). NPC's go a long way when it comes to making a good story line. For them to come off as realistic, you need to go down to the base level and write down factors for your NPC's. What do they want? What do they think? Who are they? What kind of people do they like/dislike? What actions do they condone or condemn? If you manage to write this down for all of your NPC's, your plot basically writes itself, because everyone will have an agenda (but this is usually not the desired effect, just a possitve side effect).
NPC's don't need to be good or evil, bad guys or good guys. Sometimes they're just people who want different things, and their goals collide. Maybe they want the same things and that's exactly the problem (because only one person can have it!), or they want the same things and want to go about it differently. 
Sometimes, the NPC's in a game should all be driven towards the same goal, and the opposing factor is infact not a character but perhaps a natural disaster or an occurance. 
There are many great examples of how these things can also be mixed up. 
With out NPC's, there's actually very little roleplaying apart from what ever happens between characters and what they show through their actions. Imagine a video game promoted as an RPG, but when you open it, the extent of your roleplaying is limited to your choice of fightingstyles. Sounds familiar? Don't do that to your players... 
===Step four: Dramatic factor===
In order to make things interesting, people plot against eachother all the time, but, but progress is rarely made on large enough scale for this to be interesting, the scales must be tipped, or the game rules changed. Something has to happen, someone must do something that upsets the way things are between the NPC's and the player characters, and again, this "event" must be in tune with the theme.
The dramatic factor is in other words the "push" that sends the snowball tumbling down the slope, because the snowball was already there, built by the exiting relationships, the NPC's in between. The dramatic factor should be very dependant on the plot concept. 
If the plot concept involves a princess and a dragon, the dramatic factor could be the fact that the princess is the only child of the King, and that if she isn't wed to someone, the throne will pass to the next in line, a scoundrel with no equal! 
If it's a vampire game about rulership of the city, maybe the dramatic factor is that the city has been ruled with an iron fist for generations, but that recently, the undead ruler of the city has been put to final rest when a new enemy attacked the city. Where the undead vampires might previously have been patient, now they are forced to take action and quickly, because the enemy remains undefeated! 
===Step five: The situation===
The characters must be involved somehow, and there needs to be keypoints of interest during the game that the characters somehow get into. What is the situation when the game starts? Why are the characters involved? How are they involved? You need to somehow entangle all of the PC's in the plot, to make them work towards the ending of the game. Giving them different reasons is a good idea, as it often makes room for internal conflicts, but it can be hard. In war games, it might be easy enough. The characters are soldiers, so of course they have to go. In horror games, maybe they have no choice? Some monster is out to get them, and the police wont believe them. In other cases however, it get's complicated, but it's often simpler than it seems to uncomplicate.
===Step five: The big problem===
What is it that the characters have to achieve in order to "win"? In a war game, it might be a mission they need to complete. In a horror game, maybe the only goal is to live, but in more complicated intrigue plots, they characters usually need their own agendas. There always needs to be a somewhat clear goal in the game. The characters must have atleast a faint idea about what to do, even if they do not know how to do it. "The big problem" is in other words the obstacle that needs climbing.
I have some experience with "sandbox" games, that, while offering an intriguing setting, rarely offer as interesting plot devices. I once participated in a game where the characters in question didn't have a specific goal, and while it was entertaining for a time, the entire experience was generaly not very memorable, and I'm lead to believe that this is the case with most sandbox games. 
===Step six: Key points of interests===
Also called scenes, these are the events that the game is played around. It could be the first arrival on the crime scene where the body is discovered. Later, the station, talking with the forensics guy... Ect.
It's important to realize that playing out every living second of a fictional character will get lame eventually. Skipping ahead to the points of interest is an excellent way to do things, but doing it all the time is ill adviced. Sometimes the characters should be allowed to simply go out for coffee and talk. Maybe do some shopping, or... Really anything. Sometimes you can use these random intermission sections to make an improvised scene, but otherwise, just let the players have their time "in control" once in a while.
In other words, a scene is when something happens that makes the plot thicken and there should be several choices to make in all of them, having consequenses in later scenes, and also challenges to face, that opts the players to work together and pool their resources. You need to analyze your scene closely once you've written it, and figure if you've left enough room in it. Enough freedom. Once in a while, it's okay with a "do or don't" scene, but mostly, scenes should be about choices. Analyzing your scenes, you should also figure out what possible outcomes there could be. Of course, there's usually an optimal solution, but this isn't always easy, or even possible to achieve.
Following the above advice is SUPER hard. As an experienced story teller, I find that no matter how much I try to leave many doors open for the players to choose among, the end result is often fairly similar, because in some cases, there are only so many outcomes and the real choice is how to achieve the same result. 
Characters who chose a subtle or diplomatic route might in the end have exactly the same cards on the hand one scene later as a character who prefers violence or intimidation, and this is okay, because it still leaves the players with an illusion of having made an important choice. 
===Step seven: Consequences===
If something happens in one of your scenes, how will it change the next ones? What will be different in scene 5, if the players decided to kill Mr. Lawson in Scene 2? He won't be present at the conference to accuse them of being corrupt, but on the other hand, how will his coworkers react to his absence? This example was rather extreme, and even the smallest choices should have an impact on following scenes, otherwise, what was the point of having that choice in the first place? 
In some games, it might not be prudent to lay too many consequences on the players, or they might be afraid to take any actions at all. If you're playing a game with many NPC's and a lot of travelling, remember that it's usually limited how far consequences from previous actions should follow the players. 
A word of advice based on personal experiences; I once played with a GM who at some point sent a somewhat powerful character after the players, intending to kill them. Her attempt was thwarted, but any reasons as to why she did this were completely impossible to figure out despite the players attempting to uncover this. Upon complaining, the story teller explained that the woman was trying to avenge her dead father, who had been killed by the players much earlier in the campaign, an NPC the players at this point could barely remember. While some of the players thought of this as funny after that, it had a lowsy impact on the game because it felt like an enormous waste of time. 
Gaming and roleplaying are two different things, but they can easily be combined, and usually are in tabletop games. The gaming aspects are the combat and the problem solving, where as the roleplaying is mostly the acting and dealing with moral issues and other such questionable dilemmas. Consequences should either further or hinder either of these aspects of the game. In other words, if the characters did something to help them solve a problem, that very action might have moral repercussions  for them, and on the other hand, doing the right thing isn't likely to make things easier for them all the time. Don't feel encouraged to reward players for doing the right thing. Being a good guy is a hard life, and being a moral slob, while usually easier and more rewarding at fist, often has consequences that can be emotionally devastating. 
===Step eight: Plot twist===
There should always be a plot twist. ALWAYS. If things are just what they seem, there will never be that moment when the players are taken aback, and have to question everything they did. The art of concealing the nature of the plot twist, is to make it so that it seems like the players could have found out if they had dug deeper, but giving them no reason at all to do so.
Now what is a plot twist? It's when the players who have been chasing Zhar'tan the evil necromancer all over the continent for their master, Arkharl the Conjurer, eventually discover that Zhar'tan is actually undead himself, and was turned undead by Arkharl the Conjurer, who in turn sent his minions to cover up his misdeed to hide the fact that he knows dark magic. Zhar'tan isn't redeemed by this knowledge, seeing as he still raised undead armies to slaughter civillians, but suddenly, Arkhal who might have been a mentor or father figure to the players, is brought to questioning, and the players, having had no reason to suspect Arkharl did not investigate him, even though this could possibly have lead to this discovery earlier. 
Remember that a plot twist doesn't need to turn the entire game upside down. Instead of having major M. Night Shyamalan style plot twists, consider simply adding many smaller plot twists to your campaign (not adviced if running a one-shot scenario). Sometimes it sucks when a plot twist completely turns everything around and sometimes it rocks, it depends on the players. If they players have spent a lot of time trying to get involved in the game world and have done a lot of work to build connections, having all of that taken away will probably ruin the game, but in most other cases, having a complete turn around can be exactly what the game needs. 
==General advice==
This is a collection of general advice that may or may not apply to your game. 
===Don't be a cheap ass===
Many roleplaying games rely heavily on equipment as a factor. Why? Well because humanoid creatures (as tend to be the subjects of roleplaying) are not terribly adept at doing anything really, compared to... Say, every other living being in existence. We're great at both making and using tools however. When you design your game, try to factor in that the players might be logically thinking individuals and decide to play characters who are too, and as such, they might just actually bring a gun to the knife fight for once. If your entire plot was built on the knife fight remaining a knife fight, you've failed as a story teller. 
===Don't be too generous either===
If you're too generous, you'll find yourself in an uncomfortable vacuum where, you can't crank up the difficulty without making it too difficult, but as it is, it's too easy. Remember to make your characters bleed a little if they want to acquire the good stuff, and make their rewards worthwhile instead of withholding everything they could use to solve your plot, or by pouring riches over them. 
===Regarding character death===
Every storyteller has tried this. You're in an ongoing campaign, a character dies and the game must go on... What to do? Depending on what game you're playing, character death may or may not be permanent. If it infact is... Maybe it isn't? Remember that offering up an option to cheat death isn't as silly as it sounds. It can actually be quite interesting. If cheating death is common-place in the setting you play in, remember to give the players the option to do this sooner rather than later. 
If all else fails, make sure that the player in question can be re-introduced as a meaningful character into the game sooner rather than later. 
===Deus Ex machina vs. Randomness===
Some players have raving aversions to this phenomenon. The truth is that Deus Ex Machina is actually a wide term that could apply to a lot of useful and decent plot devices, and you shouldn't be afraid to use this, especially not if you planned it ahead. The worst Deus Ex Machina situations are when the ST suddenly invokes something to counter the creativity of a player or some such. 
We've probably all had to sit through those game sessions where some ST basically played out an epic battle between two NPC's, while the player characters didn't really do anything meaningful. 
The opposite of Deus Ex Machina is when everything is decided by random factors, and this quite honestly isn't an attractive option either. While systems like D&D actually offer up ways to randomize everything from your character's name, to his race, to his age and height and weight, these tools are meant to be used as conveniences on the fly, not as a means to play your entire game by. 
Finding some measure of balance between dice and godly interventions is key to a good game. 
==="I have a problematic player" or... Maybe you are the problem?===
Both cases can hold true, even at the same time. Sometimes there are problematic players in a game, and they can continously shower your game sessions with negativity, but they usually have some reasoning behind their behavior. Sometimes, though, they're just an ill fit for your setting, your plot, your chosen system or game type or even for your playstyle. Sometimes they can't get along with other players or you in particular. Sometimes players can be unforgiving and will rather flail about and loathe the game than quit it even though the only thing they're doing is ruining the experience for everyone, and sometimes you as a storyteller need to be adamant, while at other times, you need to just accept that you did something unacceptable and that you need to repair the situation. There is no obvious solution to this, and the truth is that any player can be a problem player in a given environment, most just have the common sense and decency to decline participating in a game they know they could easily find an issue with. 
When you have a problematic player, remember that this player isn't a problem, it's his issues with your game that makes a problem. You might be able to reach some compromises with the player if you confront him with these issues he has. 
==How to handle character creation==
Sometimes players want to roleplay because they want to try out a very specific kind of character concept, and sometimes they have no clue what to play. It's actually all up to you what they play though, and what they may or may not want is technically irrelevant. Of course, if all your players have ideas for something they want to try out, launching a long campaign where they won't have the option to do so is foolish, but even if they all want something specific and you're not ready to handle that yet and instead hit them with a short 2-3 session game while you prepare, that's entirely alright. 
Remember, you're all there to have fun, but you shouldn't drop everything you have just because a certain player wants to play a character who isn't really going to work out with your current game. 
Still, remember to check with your players once in a while to see if they're having fun. 
If you can in anyway modify your game so that a new character concept actually fits in it, this is a good idea, but be sure to put some extra work into it, to flesh out the details. 
Sometimes it's better to vaguely outline what "characters" will be available. You can either make the entire character and have your players play them. It's still roleplaying, and some people prefer this way. Or, you can just feed them some background information and some "must-haves" on their character sheet and let them work out the details. 
For instance, you can tell player A that the character available is Doctor Henry Worthington, 39 years old neurologist at a hospital in Boston who comes from a long line of Doctors before him with the entire family name weighing down on him, but who secretly has a gambling problem, a drug addiction and lives a life of debauchery all as a means to escape from the pressure. Add a pre-made sheet to that, and you're good to go. 
Or, you can tell the player that he'll be playing a doctor who comes from a long line of other doctors and works at the hospital in Boston, but leave the rest up to the player. This way, you still get a doctor from that hospital if that was the point of the character, but the player is allowed to make his own character, though with some restrictions. 
Alternatively, you can make a fairly open campaign, and leave it up to the players to create characters who would be interested in participating. Say, you're running a D&D campaign about the war between to small city-states and the characters are employed by one of them. This requires the characters to adapt to a somewhat mercenary-like attitude, or for them to be patriotic enough to want to fight for their country, but apart from that, they could essentially be just about anyone. 
Some games might require more specific instructions from the ST, but still allowing much freedom, for instance, you can say that you want a Cleric, a Wizard, a Fighter and a Rogue, but the players can substitute the Wizard for a Sorcerer or any other arcane spell-caster (except for the bard), and the cleric can be replaced by any divine caster (not a paladin or ranger though), the fighter can be replaced by a barbarian, a paladin or a ranger (or any such equivalents) and the rogue can be replaced by a bard, a scout or another character with roughly equal skill sets. You can also set it in stone that the party must have a wizard for instance, but before doing something like that, try to remember that you're ordering a player to play something specific because it plays a role in your game. If a wizard is direly needed, maybe that wizard could be an NPC instead? 
Another example is, if your game requires all players to be human, for instance, or if it's not a D&D game, that all characters have an army background for instance, or that all of them are native to France (or at the very least long time inhabitants).This is alright to do, but remember that you might need to help your players, especially if what you're asking them to do might stray from their usual preferred characters. If you for instance ask all players to play elven characters, you're asking them to play a fictional race that is quite different from humans and they may need guidance. 
If you're demanding that the party in a D&D game consists of a rogue, a fighter, a cleric and a wizard (like the example above), and you have two players who really want to play fighters, consider allowing one of them to multi-class, as long as the one doing so keeps up his skill-ranks in the important skills. Maybe you could even bend the rules a little and allow a class to take ranks in a skill they cannot normally take. Bending the rules to keep your players happy is of course last resort, but it might be a good option to consider sometimes. 
Freedom is usually the better option, but it's not a luxury you can afford in every single game you play, and the level of freedom doesn't make the game. 
Sometimes putting up restrictions is a better way than to put in requirements. 
For instance, if your game takes place in a country where people of a certain nationality are currently hunted and the players are supposed to be integrated members of that society, you might consider restricting that particular nationality. Many similar cases solve problems you may have, but still allows a great deal of freedom. 
Only sandbox games have the ultimate level of freedom, but sadly, sandbox games tend to be weak in the plot department