Wipe the rims of your wheels and the brake pads off with a dry cloth (or you can use alcohol) after every rainy, muddy ride. This will help to keep the dirt and grit on the rims and the pads from acting like sandpaper and wearing out your wheel rims and brake pads faster. You should clean and lube the chain after dirty, wet rides too. Good bicycle shops recommend GT85. It cleans and lubricates at the same time. This tip is from Travis West at the Bikers Choice, Mt. Juliet bike maintenance class.
“Braking causes aluminum rims to oxidize, leaving a layer of grit that can contaminate brake pads. Every 100 miles, or more often in wet riding, wipe your rims with a dry cloth.” –Tori Boatman, owner of Gracie’s Wrench in Portland Oregon.