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I use iKlear and it seems to do the job.
 
iKlear pwns j00. works great on screen, plastics.. not harmful to screen. Or, like suggested a slightly damp cloth.
 
Get iklear if you can't figure out how to clean glass by yourself.

Otherwise use whatever other people use to clean glass and windows. Your parents should have taught you this basic skill. If not ask them. I'm serious.

EDIT: Assuming new unibody machine here. If you have the plasticbook you'll need to be much more careful and make sure your towel or cloth is wrung almost completey of moisture and use a much more diluted solution of water + non residue cleaning agent.
 
walmart's non-ammonia, non-alcohol eyeglass cleaner.

$3 for a small bottle and a microfiber cloth with free refills for life.

best value ever. much better than the ripoff that iklear is.
 
I used to work in Burger King, and they use this multi-surface / glass cleaner for general cleaning jobs. I used to use it on my iPhone's screen, literally just a tiny drip on a dry cloth, and it would have the screen looking just-out-of-the-box brand new. Shouldn't be any different for MacBook screens. Might have to try and get some again.
 
I like iKlear, but like mentioned above, if you regularly use the cloth that came with your MB with a little bit of water, that's all you need.

NEVER use anything with ammonia- I'd recommend staying away from all glass cleaners. Perhaps the new glass screens on the MB's make it possible to use regular glass cleaner, but I'm going to stay away. For what it's worth, I used a "Laptop" cleaner I got from WalMart once and it definitely hurt my whitebook screen. I'll never buy something like that again.
 
I use iKlear and this one from Monster. I got it from a friend who gets a staff discount.

They both work really well, but I like the microfiber cloth from Monster better since it's bigger and seems softer.
 
I've been trying to clean my screen with just a microfiber cloth and can't get some of the spots out. I'll try using water and hope that cleans it all up!!
 
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