If you want to have slicing blades pop up from the floor of your Incan temple, make sure you put some blood splotches and body parts around the exact spot that the blades spring from so the attentive player can sense danger. If the primary objective of your game is to kill and kill fast, do not slow the player down with boring, cumbersome puzzles. During the course of Unreal's development, I have always been harassing the level designers to make their monsters patrol a local area, have them spring out of the dark, or even crash through glass at the player. If the player walks into a room and the monsters are just standing there waiting for him, he is not going to feel that it is a very believable world. However, if he walks into a room, and his foe is just walking past him to go work on a computer terminal, he'll appreciate the extra effort that has been taken to further the believability.
Ammunition is always tricky to get right in a level.
The same rules apply to health. In Unreal, we are trying to create a sense of being in a hostile alien world. This believability is greatly helped by what I refer to as drama, things like hearing a scene occur behind a locked door, watching an evil alien punish a friendly alien, or witnessing the murder of a comrade. Drama done well will stick in the player's head for years to come. Level Heads Cliff Bleszinski has worked with Epic MegaGames since the age of 18 on titles such as the Jazz Jackrabbit series and the highly anticipated Unreal.