I spend a lot of my life at my keyboard. I write, I edit, I spend late nights and early mornings at the computer, and many, many meals. As a result, occasionally I look down and get a little disgusted. I live in a place notorious for dust, and it all finds its way onto and inside my keyboard. Spills can happen around my workspace, and sometimes they happen right on my keys. And even the oil from my fingers takes a toll: there are enough fingerprints on my keyboard to implicate me in any crime on an episode of CSI. So, time to clean!
My keyboard is not made to detach from my laptop very easily, so unless I plan to clean my computer's insides, the first thing I do is turn it upside down, balanced on my lap. Using a soft cloth, I gently brush any small particles off the keyboard surface, and give it a little shake to release anything hiding alongside a key. You can do the same, but if your keyboard is separate from the computer, make sure to detach the cable from the computer properly first.
Then, I use a can of compressed air to blow out the dust beneath the keys. Use small spurts of air, not a continuous stream, because compressed air will quickly lose its ability to blow the longer you press the button. Try to blow the dust in one direction, preferable with the keyboard on its side. Finally, I finish my cleaning by pouring just a little rubbing alcohol on the soft cloth, and wiping it across the keys. Never, ever pour liquid directly on the keys!
Oh, and don't be like me and eat near the keyboard!