Credit cards are fine if you have some self control. They are good for online purchases if they don't take paypal (Amazon). But most people end up thinking of it as another bank account they can use then get screwed over with the interest.

A good thing to do is whenever your about to buy something with a credit card ask if your willing (or can afford to) pay an extra 20% for it, or whatever your interest rate is, if not, then don't use your card.