I have discovered that just like driving your car, operating your bike for anything more than a few miles, you will start accumulating road grime that can get into your drive train, wheels and bike itself. When you get right down to it, it will start looking a bit less shiny than the day you bought it.
Before you set down to give your ride a good once over you will need:
Spray Degreaser (I use simple green)
Plenty of shop rags
An old towel
Chain Lube (I use Finish Line Dry)
Lubricant for your components (I use Tri-Flow. Not only is it a lubricant, but it also has a solvent agent in it, so it can clean and lubricate)
Chain Cleaning tool (optional, but will me your life easier)
Narrow nylon brush
Spray bottle full of 1:1 rubbing alcohol and water.
If you have a bike stand, you can count yourself lucky as you have a bit less work ahead of you, if you don't, just immobilize your ride so you can spend half an hour or so working on it. First, wipe down your entire bike with a damp cloth to remove any excess and unwanted dirt. Next, spray down all the greasy areas of your bike (the drive train, wheels, down tube, fork, seat tube). I don't recommend spraying on your hub, but instead spraying some degreaser on a shop rag and gently cleaning it until it is free from grime.
While it is working through the puddles you have splashed through and the accumulated tar the road has saw fit to spray your frame with, lay down a the old towel beneath your chain and attach your chain cleaner with an ample amount of degreaser/cleaner in the container (the above linked Park Tools kit comes with a small starter bottle). If you are not using the chain cleaner, I would suggest spraying the degreaser on the chain lightly just so it covers it and grab a couple rags in your hand and lightly cup the chain. Run it 30 or so revolutions and start cycling through the gears on the cassette as you pedal the bike. Change the now dirty cleaner/rag and repeat a couple more times until all the grime is off.
Now, take either a thin hard bristled nylon brush or a shop rag and start cleaning the cassette with a back and forth scrubbing motion until you get all the grime off.
Take another shop rag and wipe down all the joints and general areas that you have cleaned. The last thing you want is degreaser getting where you actually want grease (the hubs and bottom bracket in particular)!
Now, take your bottle of alcohol solution and spray everything you had degreased down lightly. This acts to neutralize the degreaser. Wait a few minutes for things to dry, then relube your chain with a few drops of the Dry Lube while pedaling and then start cycling through your gears to ensure everything is coated. Add a few drops of the Tri-Flow to your derailleurs to give them new life and to the pedals themselves as well. Those few drops of lube to the pedals can make a difference in effort on those long rides (when I did mine last weekend, I spun the pedals after dropping a little Tri-Flow into the pivot points just to get the agent to work in)..
Make sure the rims of your breaks are free from degreaser, if you are using clincher rims, otherwise your stopping power might become "barely slowing" power.
You now have a newly revitalized ride! What better way to finish than to polish up your aluminum rims and maybe throw a light coat of wax on there to give it a sparkle and get the rain less to adhere to.