The outside of your laptop or desktop can collect all kinds of grimy fingerprints, dust and germs. And if dust gets inside the vents of your desktop, it could slow down the functionality of the fans and other vital components. To clean your Mac, use a non-abrasive, lint-free cloth like a diaper you would use for dusting or a thin microfiber cloth that won't scratch the surface. And properly shut the computer down and unplug it before you start to clean.
You could begin with just a light dusting using a damp cloth or a dry cloth -- a Swiffer cloth works well. If you're dealing with ground-in dirt and tough smudges, you can clean with a delicate cleanser. Apple warns against using aerosol sprays, bleach, solvents or abrasives that could damage the finish [source: Apple.com]. Just like with cleaning your mouse, you should be careful not to get any moisture into the cracks and openings of your Mac. Even if it's a result of cleaning, Apple warranties do not cover water damage.