Maintaining your bicycle is important for your safety. Equipment that is worn out or in need of tightening or alignment is not dependable. Cleaning, adjustments and minor repairs are within the capabilities of most bicyclists. However, major adjustments and repairs should be done by a trained bicycle mechanic.
It is strongly encouraged you to maintain your own bike, if you have the willingness and mechanical aptitude. There are elements of bike maintenance that are fussy, and there are several bike-specific tools that are worth having even for a beginner mechanic. Park and other tool companies sell basic kits for $50-200+ that are an easy way to get most of those special tools all at once.
As a reference for bicycle maintenance, I have been happy with “Zinn and the Art of Mountain Bike Maintenance” by Lennard Zinn (there is a companion book on road bikes, and there is a fair bit of overlap between the two manuals). Zinn is pretty good about laying out basic maintenance up front, and the diagrams and instructions for doing repairs are good. Others will have other good recommendations.
I think that a good manual, a good starter toolkit and some willingness to try the repairs (experience with other mechanical stuff will help) is all you need.
Some Basic Bike Maintenance Tips:
Handlebar position
The handlebars should be tight and properly aligned with the front wheel.
Caliper hand brakes
The levers should not be able to touch the handlebars before the brakes are fully engaged and the wheel is locked. Brake shoes should have at least a 1/6-inch rubber braking surface and be centered over the rim. The nuts holding the brake shoes to the arms should be tight.
Pedals
The pedals should be firmly secured to the crank arms and turn freely. Rubber treads should be intact.
Wheels
Test for proper balance by picking the bicycle up and spinning the wheels. The wheels should not rub against any part of the frame, fender or brakes. Check to see that rims are free of rust, dents or kinks. Replace missing spokes.
Tires
The condition of the bike’s tires will affect its handling. Make sure you keep the tires pumped up to the pressure recommended in your owner’s manual. Check with a tire gauge. Replace tires when tread is worn smooth.
Chain
A chain in need of adjustment will make a cracking or grinding noise. When a chain is in its proper position, it should have approximately 1/2-inch of lag.