Nobody likes a dirty mac. Especially with the new unibody aluminum enclosures, and high gloss screens, even small fingerprints can make your beautiful MacBook old and neglected.
Things You Will Need
Mac-safe Cleaner / Polish
Lint Free Cloth
The first thing to do is to find an Apple specific cleaning
solution. Any old 409 or windex WILL NOT do. This is because the plastic cover over the screen and the aluminum are very susceptible to coercion. iKlear makes a great product called apple polish, but any equivalent will do.
Next, you want to find a lint free cloth, preferably one that you use exclusively for cleaning your macbook. Make sure it's clean and if you use it often it's been washed since the last time you used it. Generally a light soap and water will suffice.
For the body, spray your polish on the cloth, making it damp. Clean as you would any other object.
For the screen, you'll need to be more meticulous. Spray a light coating of your polish on the screen then clean either top to bottom or side to side. Your tendency will be to just make swirls or clean as you feel. DO NOT GIVE IN TO THIS TEMPTATION. The screen on MacBooks can gather small scratches that over time will show themselves.
Finally you'll need compressed air to get all the crumbs and dust out from the keyboard. I don't recommend using a straw and trying to blow the dust out yourself, as it's very likely you'll add more than you get out.
If you follow these simple steps, you should find yourself with a beautiful MacBook - Fresh and Clean.
Tips & Warnings
I would recommend having a clear hard surface to place your MacBook on during the cleaning process. Especially when you're cleaning your screen. Whatever you do, don't place your screen on your lap or a soft surface when you clean it. The pressure from cleaning can CRACK your MacBook's screen. For best and the safest results, place your screen (cover-down) on a hard smooth surface, like a desk.