So what might be a good reason to open a credit card? Well, one reason is to build credit. Everyone has a credit score that is used to show lending agencies what kind of credit history you have. If you have a lot of unpaid credit cards, or even multiple late payments, this poorly affects your credit score. If however you use a credit card, and other loans, wisely you build a good credit score. A good credit score will help you when you go to purchase or lease a car or buy a home. In order to have a credit score you need to have a credit history and this is where a credit card can be good. If you pay off your entire bill every month (essentially use it like a debit card) then you will start to build a history of having good credit skills.
If you ever find yourself in over your head with credit card bill you should at least pay the minimum balance. While you will still be charged interest, this does not affect your credit score as badly. Make sure that you save every penny and pay off the entire balance as soon as possible.
Here are some great resources for credit info: