Every morning, I wipe out the external keyboard with water-moist paper-towel at my work place. So, I don't like a dirty keyboard.
The best policy would be to prevent staining from the beginning.
I wash my hands as frequently as possible (without being noticed as OCD-like by my coworkers).
Moist paper-towel should do the job, except for some nasty stuff you managed to put on your keyboard. My portables (except for my work PC Dell, which does not get my love) have the keyboard protectors on.