Congratulations and Good Luck!
You won't find it any harder than high school
I can't disagree with this statement more. I am about 15 years older than the kids coming in from high school who make up about 2/3 of the student body at my college. They usually get a healthy dose of "oh crap" and then start taking their work seriously, or else they drop out. Not all of the kids are this way, but far too many are.
I have a few pointers for you:
1) Organization is your friend. Being sloppy with handouts, homework, notes (you will take those right?), etc. is a sure way to get behind or to simply lose out on points because of lost assignments or forgoten homework. So, get yourself a system. Make it work for you and stick to it. Make sure your organization system is expandable. I like to have a 3 ring 1.5" thick binder for every class. The kind with the clear fronts so that I can print up a title page and put it in the sleeve for identification. Works wonders when you are rushed and trying to get the right materials out of a backpack because you can see at a glance what class the binder is for. Get a 3 hole punch. Punch everything that gets handed to you by an instructor, and put it in its place in the binder. Loose leaf 3 ring notebook paper goes great in there for taking notes.
2) As others have said, time management is crucial. Also, keep in mind that the first few weeks are usually on overload with assignments, so it doesn't hurt at all to read the first one or two chapters from all of your text books just to get a jump on things. You might not end up needing to have done it, but from experience I can tell you that in my case 9 times out of ten it helped to be ahead.
3) A lot of your grade in a class can be based on subjective things. Do your very best to present yourself as a student who really wants to learn and who appreciates the opportunity to be in the instructor's class. Not only does that put you in the best frame of mind for learning, but it will help to impress your teacher and they will be more willing to help you out. Try to get to know them at least a little and show them you are friendly and can be relied upon. NEVER show up late. NEVER let you cell phone ring in a class. It disrespects the instructor and your fellow students. I have seen bad things happen to people who don't follow that advice. Related to that, if class gets dismissed early, sometimes that is a great opportunity for you to get some on-on-one time with the instructor to ask questions. Side benefit - they will think you are cool that you don't want to ditch their class even if you are allowed to. I actually had this happen to me today and got some commendation for creating an experimental network lab setup and implementing it with the extra time the instructor had given us. I could have just left like many of the others.
Anyway, hope that helps,
Enjoy college!
LDB