Adventures should MOVE. Something should always be happening to (or because of) the PCs. If 20 minutes have passed without some kind of conflict or confrontation, throw something in there. You have the entire human imagination at your disposal - don't waste time on unproductive dead ends!
I absorbed this idea in its entirety from the first (and best) edition of the Star Wars RPG published by West End Games. Greg Costikyan is a genius.
DISLIKE: USING MAPS
This is a limited dislike, but a strong one. If I'm running a game, I don't want to use tactical maps. They slow down play, they pull the players' attention away from their own imaginations, and they make it harder for me to improvise some cunning last-minute thing. Tactical maps (and building/dungeon/structure maps) limit your options, which undercuts one of the great advantages of RPGs - the ability to expand your options with a thought. When possible, I avoid using tactical maps. When not possible, I try to use them purely for positional reference instead of for accurate simulation.
Except when I'm running Marvel or Champions. I do love simulating superhero combat.
And I'm a huge fan of world maps. They're great idea-generation machines.
This one probably traces back to Star Wars also. I like their abstract method of handling starship combat; it's much more exciting than actually figuring out the positions and trajectories and stuff. I'm all for simulation - but only if we're simulating fun things. Let's not simulate physics, people.