Financial Aid
Get on financial aid ASAP. It will make your financial situation less tight, even if it will cost you some extra money later. The Department of Education has the Direct Loan program. Use it. If you're eligible for scholarships, go for them. Apply for as many as possible. Nothing is better than free money paying your tuition.
Sex
Have condoms near your bed. You don't need to have them out, but keep them near the bed. Even if you're not in a relationship, even if you don't plan on having sex, stuff happens. Things may get wilder than you expect. If you don't want to get babies or diseases, have condoms handy. And if you don't end up having sex, they make fun party balloons. Don't sleep with anyone that says no to a condom. If they don't like it, they can go get a venereal disease from someone else.
Academics
GO TO CLASS! If you don't go to class, you won't pass the tests. And if you don't pass the tests, you won't pass the course. And if you don't pass your courses, you'll fail out. And that just sucks.
When you go to class, pay attention. Listen to what the professor is saying, listen to questions that other students ask. If you ever need something clarified, ask. The professor is there to facillitate your learning, and if you don't ask questions, they'll assume you understood them.
When you don't understand something big, see the professor during their office hours. Office hours are there mainly so students can stop by and ask questions. Make use of this.
Social Life
Find a group of friends. Your first year, your circle of friends will probably mostly be people in your classes, but in your second year you'll drift more to people who aren't in your classes, people you know from social events or clubs.
Join clubs. If you want to join a frat, go to their recruitment events. Go to school-sponsored events. If you're into sports, go to the games for the sports you like. Enroll in PE activities.
Go to parties. Not all parties are good. Parties with people you know are better than parties with people you don't know. Be wary of going to a party where you know no one there. If you drink, try not to get drunk. Unpredictable and unforseeable things happen when people are drunk (re-read Sex above). If you have a drink, whether it's alcoholic or not, don't put it down. It doesn't happen that often, but people do sometimes put drugs in drinks. Don't let it happen to you. If you're tired of drinking a particular beverage, put the cup/bottle down (or dump it) and don't touch it again.
Roommates
If you're living in the dorms, you will probably have a roommate for at least your first year. You need to draw up a roommate agreement with him regardless of whether or not your school requires it. The roommate agreement will set in writing the policies for the room which both residents will be expected to follow. Remember, there's several things you should include on such an agreement, such as visitors (and overnight visitors), official quiet hours, what sort of things will be allowed in the room (cigarettes, etc.), and how you will share each other's belongings (if any sharing is allowed at all). Write it up, sign it, have your roommate sign it, photocopy it twice, one for your roommate and the other for your RA. You should give your RA a copy just in case suddenly both your copy and your roommate's copy disappear.
Parents
Unless your university is next door, you probably won't see your parents every day. If it's in another state, you might only see them a few times a year. Get used to it. If you're close to your parents, email or call them often. If you're not that close, do it regularly, even if it's not every day. Keep in touch with your parents. They love you, and whether or not that is reciprocated, they will like to hear from you from time to time. And chances are, they're paying the difference in your tuition after loans, grants and scholarships, so there's financial reasons to keep in touch also.
Rules
There will be rules on campus, in your program and in the dorms. Follow them. Not following them tends to have unpleasant consequences (ie finding out that your housing contract is not renewed, being put on probation, being expelled and banned from campus, et al).
Working
If you need extra money, get a job. School comes first, but working 20 hours a week should be OK if you're a hard worker. You shouldn't go too far over 20, because then you'll have to balance classwork, your job and sleep, and any attempt to balance the three is going to be messy and make you physically ill. When looking for a job, check the student employment office if there is one for a list of openings. Food service jobs are OK. Janitoral jobs are OK. Do not say no to a job simply because you think it is below you. Being unemployed usually doesn't pay anywhere near as well as flipping burgers at the cafeteria.
Freedom
You will be free to do pretty much whatever you want (except for things prohibited by the university's rules and things that are illegal). You will need to actively choose to go to your classes or not, to go to your clubs or not, etc. You will be responsible for yourself and how you behave. You will be treated as an adult, and as such you are expected to behave like one. It's your responsibility to get your work done, to do your job if you have one, to go to clubs if you're in any, what have you. You will probably need to budget your time to effectively fulfill all of your responsibilities.
This is by far the hardest thing for new college students, having to deal with their newfound freedom. Give it your all and you should be OK.