Completely cleaning a bicycle is either expensive and time consuming or knowledge intensive. Here is a cheap and fast method for cleaning your bike.
This method allows you to clean the frame, gears, derailleurs, chain and wheels without taking parts off the bike.
Step 1: Collect tools
You will need a degreaser (I use shout the laundry cleaner), a power washer, oil (do not use wd40) and a wet dry vac.
Step 2: Really dirty bike
If the bike is really dirty power wash it first. Please, be careful that you don't use a very tight/powerful setting. You want to avoid ripping the paint off of the bike.
Step 3: Fairly ditry bike
Spray the degreaser on the parts of the bike that are dirity. I like to use Shout! becuase it is fairly viscous and will not easily drip off the bike.
Step 4: Pressure wash bike
After waiting about ten minutes user the presure washer on the bike. You should be able to get into the parts that you can't with your fingers.
Step 5: Check for cleanleness
If the bike is not clean enough for you go back to step two. If it is go to next step.
Step 6: Vacume bike
Use a wet dry vac to dry off the bike.
Step 7: Oil chain and derailleurs
Oil the chain and both deraillerus. After you have oiled the chain take a rag and wipe off chain.
Step 8: Ride bike
Take your bike for a nice ride.