I clean the keyboard (and basically the hole notebook including screen) with moist desinfecting alcohol wipes. Just be careful on the left side where the ports are. The labeling there is coming of, if you use such "strong" stuff. (Mid 2010 Macbook Pro) I also do this with the flat white Apple-Keyboard every month, to keep it white. I know this might sound hard, if you read the manual it will definately suggest some other way to clean your keys.