Congrats on your first credit card! Just keep these two rules in mind, and you won't get yourself in trouble:
1) Don't buy things with a credit card that you can't afford! It should be painfully obvious, but some people just don't seem to understand that you have to pay off these things eventually. The longer you wait, the more it will cost you.
Personally, I don't buy big ticket items with a credit card unless I have at least TWICE that amount in the bank. I want to be certain that I can pay off that statement in a week or two after it comes in the mail, even if I run into some unexpected money problems along the way.
2) Pay off your credit card balance IN FULL whenever possible. Credit card interest rates are usually much higher than any other kind of loan, and can quickly add to your outstanding balance. Of course, if you follow rule #1, you'll have no problem with rule #2.
Also, one final tip... Don't rush to pay off your credit card bill before the due date! Ok, this is a bit controversial, but hear me out. When you get your credit card bill, you usually have 2 or 3 weeks to send it in. If you wait a week or two to pay off the bill, it gives your money some extra time to earn interest in the bank.  If you send in the check right away, that interest ends up in the credit card companies' bank instead! I don't know about you, but I WANT that extra buck or two of interest! It usually takes less than four biz days for your check to arrive to your credit card company, so you can wait to send your money in until a week before the due date.