How to wash a bike properly?
Cycling Tips has some useful pointers.

To summarize:


Degrease the drivetrain.
Wash the degreaser off the drivetrain with the brush and sponge.
Wash the rest of the bike with soapy water and the sponge.
Rinse the bike off with the clean
water and sponge (or a low pressure
hose).
You can dry the bike by wiping it
down with a cloth or let it air dry.
It’s a matter of preference.
Finish the frame off with Armor-All
or give a light wipe with silicon
spray to deter the next lot of mud or
dust from sticking to the frame too
quickly.  For obvious reasons don’t
wipe on the handlebars, brake hoods,
saddle, or wheels.