I don't do random encounters.

If a group's wandering around in the wilderness, I know what sorts of things are out there, and therefore what the PCs are likely to run into when I decide an encounter is warranted. If they're wandering around town, same thing. Dungeon? I know the inhabitants and their schedules, so I have a pretty good idea what'll be where, when.

Not everything's scheduled, of course. But the characters' actions generally tell me when it's time for an encounter. Once in a while, they take an unexpected path and I improvise a bit, but it's still not random. They're not going to stumble across a pack of gnolls because a chart somewhere says so.