Copy and pasted from doityourself.com
To begin cleaning the tap you will
need to get keg tap detergent and mix
it with water. Check with your
local liquor store to see if they
carry a cleaning kit for a tap. The
instructions on the kit will be able
to tell you how much cleaning
detergent and water needs to be mixed
together. The mixture should be put
into some sort of bottle that has a
hand pump to produce the cleaning
solution.
Find the tap's faucet and remove the
knob. Once you have done that, you
will need to put the knob, the faucet
and the hose that produces the beer,
into a bucket.
Find the cleaning attachment in your
kit and connect it to the faucet. Take
the bucket with the other parts in it
and place it under the main part of
the keg. Then put the hose inside the
bucket so the cleaning solution will
be able to steam into the bucket.
You are now ready to pump the cleaning
solution into the bucket. It is best
to let the solution sit in the hose
for a good amount of time to make sure
that all bacteria is broken down. Your
kit will tell you how long to soak the
hose.
Take the bottle you used to pump the
detergent and clean it thoroughly.
Fill it with cold water (without any
detergent) and pump the entire bottle
of water into the hose. Use the other
tools included in your kit, such as a
wrench to unscrew the facuet and use
the brush to clean out the keg and the
faucet.
Rinse all the materials with cold
water and allow them to dry completely
before reassembling the unit.
Now that your keg tap is clean, it can
be put into storage to await your next
party.