Turn off the computer and unplug electrical cords. (For a laptop, remove the battery.) Pour a little rubbing alcohol into a bowl, dip in a foam swab (foam won’t leave lint behind like a cotton swab can), and then very carefully run the swab over all speaker holes, cord inputs, vents and any other openings on the monitor; follow up with a dry swab. Barely dampen an eyeglass cloth (or any other soft, lint-free cloth) with water and give the rest of the exterior a once-over. (For stains, add a drop of dish soap to a fresh cloth and rub; use the damp cloth to wipe clean.)
Wipe the screen from top to bottom with the barely damp cloth. Even if you don’t see crumbs, turn the keyboard upside down over a wastebasket and give it a few gentle shakes—particles may be hiding under the keys. Keep the keyboard upside down, hold a can of compressed air upright with your other hand, and shoot a few bursts in and around the gaps between the keys. This will whisk away dust. (A small paintbrush also does a decent job.)
Minutes 3 and 4:
With a new alcohol-dipped swab, trace the outside of each key. Then swipe the tops of the keys gently with a fresh cloth dampened with rubbing alcohol; there’s no need to press down.
With the rubbing-alcohol cloth, tackle the mouse, including the bottom. If it has a red light underneath, shoot a puff of compressed air in there; if it has a trackball, spin the ball a few times with your cloth. Turn the computer back on and get going on that brilliant novel/to-do list/e-mail you’ve been putting off.