Trying to over-specify goals and whatnot is the #1 killer of new communities. It's best to let things develop organically with a bit of guidance from mods/admins and the community to keep jerks and Nazi nonsense out. An image of a specification will emerge by the time it's necessary to specify to keep things from getting out of hand.
Yeah, focus more on the 'away from' than the 'towards'; don't aim for anything in particular, just line out the few things you definitely want to avoid and otherwise let it develop how it will. :)