wash your car once a week. eagle one makes great chrome and aluminum wheel cleaner. use that along with a soft wheel brush. between washings, keep a bottle of window cleaner and spray wax in your trunk. i had chrome rims on my old car and i used to clean them every day with window cleaner and put a coat of spray wax over top of that. it will give your rims the ultimate glow.
Yup eagle one wheel cleaner then top it off with a wax. Wax makes cleaning them a lot easier and helps reduce the amount of brake dust and road grime thats able to attach itself to the rims.
Mothers' chrome polish works miracles on chrome wheels. I use it once every 3 or 4 washes and just clean them normally in between and they shine like new.