While that's getting whittled down, I'm going to start another discussion about more specifics...
A lot of what I'm going to be running will likely be based off of published modules and those in
Dungeon, though I've no problem with tweaking a bit. And once the game "takes off," I'm more than happy to let the players take the reigns and leave the modules behind...
As far as how I work a campaign, I tend not to have any giant story arcs looming; I'm not a big fan of "save the world" campaigns, because they generally seem to get a bit railroaded. What I do try to do is just have things happening that the PC's can get involved in, all over the place. Keeping in mind that what they ignore doesn't just go away.

Umm... anything else? Not that I can think of. Let me know if I've left anything out you'd like to know.
[Edit] I remembered something else. At the beginning of the campaign, it's the only time I don't really give complete free reign. Once I know the generalities of what the players want out of the campaign, I generally pick out the first adventure, and ask the players to build their characters according to some general guidelines - just helps it get off the ground, I've found. Because I really don't like games where the PC's meet, and become best friends, the guidelines are generally only rigid enough to make sure they already know each other for some reason.