Becky,
Ol'89r nailed the answer right on the head. Read the service manual, then read it again. It should give you some type of service schedule to follow. Remember, no matter how well you maintain a bike, parts will still wear out. However, by following a proper maintainance schedule you will be able to help alleviate most of the break downs caused by poor maintainance.
One last thing, always go by the manual (or advice from a certified mechanic) and not by "word of mouth" from some half baked yo-yo spouting information like they know it all, when all they really have a grasp on is wiping their noses, and keeping their shoes tied.
Your Pal,
Mully
PS: The only dumb question is the one never asked........