I've been trying to harness some awesome inspiration I recently acquired and have come to an interesting observation (at least to me).
Normally, I enjoy rolling on random tables and rolling up stats randomly. I like this as a first step, because it often fires up my imagination once I start seeing the stats or looking at the raw data. An excellent example of this is James Raggi's Random Esoteric Creature Generator. A few rolls on these tables and an awesomely grotesque--and completely unique--creature is staring back at me from inside my mind. Character creation is much the same way. Perhaps my only real reason for liking "3d6 in order" is that it instantly throws into my mind at least one image of a character. It feels like that character already exists, in fact, that the numbers already existed and were somehow channeled onto the character sheet from some PC-Limbo where my new dungeon delver was waiting.
What I find funny, however, is that I'm much less competent at looking at the raw and finding the story in it when it comes to dungeon maps. Other maps? No problem. But for some reason, I've found that drawing the dungeon first doesn't really fire my imagination. I end up with lame maps full of squares. On the other hand, coming up with a story, or even just a cool title, almost always helps me make a much cooler dungeon, full of secret passageways, magical portals, pits of ooze, etc.
So how do other people handle this? Which comes first for you, when creating a dungeon or other adventure.