Keeping your bicycle clean is without a doubt the single most important act involved in preventive maintenance.
Sand, mud, grit, grime can cause an unbelievable amount of wear on the bike's components.
Cleaning the bike allows you to examine your bike close up for wear and tear.
There are many that will tell you a dirt free bike is faster.
I know mine always seems to have a little extra power right after I clean and lube it.
Cleaning allows you to get a real close look at the parts of the bike and determine whether or not there is anything that needs replaced.
This means you can replace a worn or damaged part before it breaks on a ride and you have to walk back, bike in tow.
The general rule is that if you ride 4 or more times a week you should clean the bike weekly, less than 4 and you can do it every couple of weeks.
I put together a separate report a few months back that details how to clean the bike and what to look for during inspection process.
While you are cleaning your bike you should be looking for things such as cracks, rust, cracked or buckled paint, loose handlebar tape, missing or sharp teeth on the cassette, check the tires for cuts and slices, and make sure the hub is tight.
It is also a good time to check to see if the chain is stretched and may need replaced or if the brake cables or pads need some adjustment etc.
After cleaning the bike and the drivetrain make sure to lube the bike.
The general rule for lubrication of the chain is to use 1 drop per link and wipe off the excess.
I have also found that it is best if you can leave the bike sit for at least a couple of hours and even a full day after lubrication before riding so the chain will dry somewhat.
This will help keep the chain cleaner as when the chain is drier it attracts less dirt and grime.
Cables for the brakes and shifters can work loose over time.
Check these each time you clean the bike.
Usually these can be adjusted with very little effort.
If they show a great deal of wear they should be replaced depending on your bicycle maintenance skill level you can do that yourself or have a shop do it.
If you like to tinker with stuff like I do, then you will probably do it yourself.
When cleaning your Road or Racing Bike you should check the handlebar tape for tears and such and whether it is tight etc.
New tape is pretty reasonable but if the old tape is still good but just a little loose you can usually fix it with some electrical tape.
With electrical and duct tape now coming in several colors you can probably even find a matching color.
The bar tape on my Giant happened to be black and I used black electrical tape to fix a small tear as well as at the ends.
It seems to be holding up quite well.
If your cassette or crank is showing a good deal of wear or has broken teeth, you will probably want to have a shop look at it since most of these require special tools such as chainwhip wrenches and crankarm removal tools.
Keeping the bike clean and doing regular inspections can have a great impact of the life of your ride and how much time you spend enjoying the ride instead of waiting for it to be repaired.