I wish I had had some experience living "on my own" before going to college. By this I mean something like spending a few weeks at summer camp... before I got to college I'd never been away from my parents for longer than a week at a time. (Can you say overprotective?
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I agree with AOIIalum, go to every class, and take good notes. It makes a world of difference.
As for credit cards, well, for some things you need a CC, and it's safer to carry a CC than wads of cash. Just be sure to pay them in full every month. American Express actually requires you to do this. And set yourself a budget - and stick to it.