Bikes are inexpensive to maintain. And we at Salvagetti want you to be happy, so we have a short list of how to save a pretty decent amount of money while having a better running bike.
In order of the magnitude of how much money you will save:
1. Replace your chain before it is too stretched out. After a chain stretches, it acts as a hammer on your gears and derailleur. Once a chain is TOO worn out, you have to replace the whole drivetrain because the new chain will not interact nicely with your old stuff. Chains can safely stretch to about 0.75% growth before they should be changed out. Drivetrains *can* last several chains...
Money savings - $100 to a huge amount depending on how fancy of a bike you have.
2. Wipe off your chain after rides. This removes the nasty stuff that causes the chain to wear out. After you wipe your chain, look to see if it looks like in needs lube. It should look sweaty if it is lubed properly. After you lube your chain, let the chain soak in the lube before wiping it down.
Money saving potential - see above.
3. Pump up your tires - This saves your energy. This make the tire act like the experts have designed it. Tubes aren't all that expensive to replace, but wheels (which a properly inflated tire protects quite well) can get very pricy. Road tires also are going to give you more miles if they are properly inflated when in use. Pump up your road tires before each ride. Mountain tires should be checked about every 2 to 4 days.
Money saving potential - $5 to the cost of wheels.
4. Don't skimp on tires - This is one of those touchy subjects for some. Tires, like the Continental Ultra Sport ($16 MSRP) are great tires, BUT NOT FOR DENVER. Getting a slightly more thorn resistant tire will end up saving you more than the difference in price. A great Continental Tire for the money is the Ultra Gatorskin ($40 MSRP). In addition to you not visiting the bike shop for flats, you will also get more miles for the dollar and have a better riding bike the whole time. The Gatorskin is a *less expensive* option.
Money saving potential - $5 to who know how many flats you could get with one tire.
Please feel free to post other ideas for maintenance that pay you back.