Firstly, clean room wiper and Windex. Buy a pack of clean room wipes on eBay for ten or fifteen bucks, they will last a very long time. Very tiny bit of Windex, and apply to the wipe - NOT THE SCREEN!
Secondly, and this will get thumbed down but it needs to be mentioned; please don't be nasty. This is a two thousand dollar computer. So many people leave grease on their hands from eating, or don't wash their hands, and touch the computer. If you're eating with your left hand, limit touching the computer to your right hand, or vice versa. Wash your hands before and after a meal, and before/after using your computer. If you feel like your hands are sweaty or greasy from work, touching outside objects, or food, wash them before touching your computer. I am a complete mess as a human being, but my four year old laptop has no grease or dirt on it - a testament to how this basic system can keep clean even the worst of pigs.
This should be done out of respect for the computer. Maybe you hate your computer - if this is the case, then just do it out of a desire to not be nasty. This should be a strong internal desire for everyone. This is all basic hygiene. Here are some pictures of things we see every day. There is no reason with the proliferation of indoor plumbing and handsoaps for people to have devices that are dark brown with dirt or have bugs crawling out of them. :(