C&C Campaign Issues

I'm trying to put some forethought into running a C&C campaign. Here are things I have been thinking about:

Is there an overall plot to the campaign or is it just about dungeon crawling or is there some happy medium I can reach between the two?

Should I have a small, intimate party or large numbers of miscellaneous yahoos?

Start at level 1 or not?

If people miss sessions, are they just out of luck or should I slide them some XP or goodies so they can maybe keep up?

What am I going to hand out xp for?

Should we even bother calculating XP in the traditional way?

Are we going to keep track of time in the Gygaxian Grognard format or play fast and loose with things?

Should the campaign be strictly by-the-book? If not what house rules will we use?

Will the players be able to use game mechanics from other d20 products?

What setting should I use? Greyhawk? I'd kinda like some new areas to explore, maybe with an only partially complete map at the start of play.