How does one take care of white leather shoes?

I have a nice pair of white Puma sneakers that are starting to show their age. The rubber sole is starting to get dark, the top is getting a little scratched, etc. Do you have any good tips for maintaining or cleaning shoes like this?

Do you have ideas on how to keep them smelling fresh? How about getting rid of dark stains on the leather? How do you get the laces clean? What about keeping the inside heel from wearing down?