I pull the keycaps and clean them in 1 tsp of powdered laundry detergent + 1 tsp of "Oxi-" or "Biz" in a liter of hot water - and rinse thoroughly.
Vacuum out the tray (suck, don't blow) and then alcohol on paper towels and/or Q-tips for the stubborn stuff.
Wipe down everything else with paper towels and alcohol and that should take care of 99% of it.