In the games I GM, I'm very much a planner; I set the environments, the NPCs, basically everything beforehand, and don't tell my players until they go to explore them. Then, my games are mystery games, so perhaps that comes with the territory.

When playing, I like games that have clear, up-front environments and settings as well; I don't find it limits imagination, but simply gives me something to springboard from.

Both as a player and as a GM, I always make sure that the game/character was built with a few general plots in mind, into which to specialise as the game unfolds.