All suggestions are good, except I want to stress one thing: Do not allow yourself to be fooled by your "minimum payment". I learned that the hard way, and so have many others.
The minimum payment is DELIBERATELY structured so that when you go and charge $400 on something, you get your statement and see a very low minimum payment. It will be ridiculously low, and that is so you will feel that you can afford to go out and charge more, 'carrying' a lot of debt from month to month. This is how most people get into credit trouble, contrary to those who claim its because people aren't paid enough by 'greedy corporations' and thus have to resort to credit to pay rent, buy food, necessities, etc. Nonsense, that happens, but its the exception and not the rule.
What you are paying in that minimum payment is largely the interest only, so if you only make the minimum payment, you're paying little on the prinicipal amount you charged (the $400). You could easily end-up paying $1500 for something that was only $400 to begin with.
This all seems so obvious now, but I was young and not too wise when I got my first credit card. Learn from my mistake. Credit can be a very beneficial thing, if you understand it and use it wisely, but it can be your nightmare if you don't.