Since Shieldhaven brought it up in the comments on this post, I should talk a little about what I do when it comes to dungeon-running.
I grew up playing my dad's AD&D games, which were always dungeons. I think I've only run one game that was not a dungeon, and that one was a one shot for a single player. Contrariwise, except for my dad's game, I don't think I've played another D&D game that has been primarily dungeon based. So I guess it is still a little odd that for me, when I am running a game, dungeon exploration is pretty much everything. Which isn't to say that the world above doesn't matter-- it certainly does. Just that the players won't typically be interacting with it directly; at least, not for some time.
The part that can be chalked up to laziness is where I like the constraints that dungeons put on the party's immediate actions, at game start. There's this map, see? There's only so many directions they can go. I don't suddenly have to gen up a bunch of stuff I'm not prepared for (unless I haven't read my notes in a while, which has certainly happened), or come up with a more artificial way to use something I'd planned. What's there is there.
That said, no one really wants to go through another boring hall after boring hall, fighting incongruous monsters and improbable traps that don't seem to have any reason to be there. Also, there's the problem where you find a bunch of loot that is difficult to impossible to spend, because there's not a ton of good shopping in the underground. Usually. So here's a list of things I think about when I'm preparing a dungeoncrawl campaign.