The most important thing is to you pay all your bills on time, all the time. It doesn't really matter if it is a small amount or large, as long as you do not default on any payment. The following website explains the criteria the credit reporting agencies use in rating your credit score:
But in general, there are a number of things you need to be aware of in building a new credit history. The following MSN Money article explaining these steps.
Hope this helps.