While you might be tempted to spray your bicycle off using a garden hose, that's not necessary unless your bike has an inordinate amount of mud caked on it. Usually, just wiping your bike down once a week or once a month -- depending on how often you ride -- is enough to maintain it. For the parts that get gummy from grease and oil, isopropyl alcohol is a useful solvent that will clean away the sticky mess almost effortlessly.
Dampen about a quarter of a cloth rag with alcohol.
Wipe down the brake pads of your bike with the alcohol-dampened cloth, removing all the dirt and residue that has built up.
Use a clean rag and more alcohol to clean the rotors. Wipe off the outer surface, then cover your finger with a damp section of the cloth and use it to poke in between the spokes and clean the grime from around the inner part of the rotors.
Dip an old toothbrush in isopropyl alcohol and use it to scrub your bike chain clean when it becomes encrusted with oil and dirt. Thoroughly lubricate the chain again with bike oil after cleaning it with alcohol.
Remove the disk brake pads if they become contaminated with oil and soak them in isopropyl alcohol. You don't need to submerge them and leave them sitting in the alcohol; simply pour on the alcohol to saturate them. Allow the brake pads to dry for about five minutes, then lightly scuff them with sandpaper before replacing them on the caliper.
Wipe off the rims of your bike using the alcohol and another clean rag.