I clean my PB screen using the iKlear cleaner. It's like $20 at your local Apple Store or at the online store at that link and it comes with two chamois cloths and some cleaning fluid +extras. It works really well, imo. Good luck!
They work great and remove _all_ keyboard marks from your screen.
If you can't afford 2.49 for a 2-pack that'll last you forever, damp paper towels will work too.
Don't be afraid of adding water, as long as the computer is off and you dry it well you'll be fine, just don't use Windex...it'll take the anti-glare coat off.