Ade gave some very good advice in the last point.
Yep. I remember my freshman year of college. I had gone to public school for the past twelve years before that, and I was used to yard duties ushering students to class, calling in sick, forgotten books being dropped off at the switchboard by parents, parent-teacher conferences, and the like. Education was compulsory, and if you weren't in school or were doing poorly, somebody was going to hunt you down and get to the bottom of things. That's just not true in college.
There are no yard duties yelling at you to go to class (though there are helpers around on the first few days of class so you don't get lost). You can e-mail your teachers that you're too sick to go to class if you want, but that might not be an excuse and your grade will suffer. Forgot your books or assignments? Too bad - your teacher may be nice and accept it late (with a grade reduction), or s/he might not accept it at all and you'll get a big fat zero for a grade. You're not going to class or are flunking your classes? Well, unless you have a scholarship or some other agreement with the school where good grades are mandatory to keep attending school, nobody will care. Sure, the registrar will advise you of your lack of credits earned, but as long as you are paying your tuition and other expenses, the college couldn't care less.
You can always spot the kids who are totally unprepared for college. "But I didn't know!" is like their catchphrase.

It's your
job to know. Ignorance of the law is no excuse, and so is ignorance of university policy.