Sprits with a little water if need be. Or cleaning spray like iClean/iKlear--though that's not really needed for the iPad. Just for tvs etc. with coatings where you don't want to use windex and water may streak.
Microfiber cloth for the finger prints. A very slightly damp cloth or soft paper towel for the stuff that does not come off without dissolving it. A microfiber cloth may not remove all things on the iPad. If you have to rub too hard, use a little dampness.