Well, you might want to have 2 cloth when cleaning. 1 cloth wet to clean the screen, another 1 dry to wipe off. Wiping off prevents the water stains/streaking.

As for the dust issues, wiping tends to cause static and that causes dust to "stick" on the screen. You could use cleaning solutions such as iKlear or one of Radtech's solutions to prevent static but do keep in mind that you'll still need to clean from time to time. I personally wouldn't bother with the solutions, water seems to work fine, just that you might need to clean often.

Compressed air. They usually come with the narrow tips to direct into the area under the keys.

Or you could pop up the individual keys and get a vacuum over it. Just be careful you don't lose keys and bend the pins.