It is simply one man's opinions. I feel its easiest to just jump on in with an example rather than try to explain the bits and pieces of the system. Let's start with the simplest of quests newbie guildmaster quests. Players can go to the store and buy 4 bone chips or have a friend give them a bunch of them and sit there and do this quest again and again. Raising their faction, gaining some items, and getting free experience.
Player walks to the guildmaster and asks for a quest.
Rather than give him the bone chip quest every time the guildmaster chooses from a list of preset quests. One might be the 4 bone chip quest, another might be to run deliver a note, another might be to bring back another item etc. Once the guildmaster gives the player a quest he will not give him another one for a certain period of playtime. There would need to be a few new variables attached to the player file which would handle which quest they were on and when the time limit would expire. First being the quest number that the player is on, the second would be the time limit when this quest will expire.