1. Buy all of your textbooks before classes
I used to wait until after my first class and make sure that the textbook was required, but there were times I would have a homework assignment due before I would receive the textbook. It's better to buy/rent all of your textbooks in advance and then you can always return ones that you don't need and get a refund.
2. Make sure your schedule is set
Obviously there could be some changes that need to be made during the drop/add period, but make sure your schedule is all set. Try to memorize your schedule so you can have a mental plan of when your available for other activities.
3. Scope out where your classes are.
Find out how long it would take you from your dorm, the dining hall, and from class to class so you know how long you have to procrastinate between classes. I typically get stopped by one friend or another to catch up on the way from class, so I have to know how much time I can spare to get to my next class on time.
4. Buy a good planner.
Whether you have 15 different obligations or 5, get a planner. Figure out what you want in one before buying a random one at Walmart so that you know you will actually use it. I bought a really simple one from Walmart that is thin like a regular notebook and has weekly and monthly calendars, as well as a section in each week for notes. This works for me because the lines in each day are wide enough that I don't feel like I have to cram everything into small spaces and can actually read what I have to do each day.
5. Get all of your supplies ASAP.
If you need a new calculator, batteries, notebooks, pens, or pencils, get them. Don't be the kid that constantly has to ask for a piece of paper or a pen. Have a different notebook for each class, or get one of the multi-subject notebooks to keep yourself organized.
6. Live by your syllabus
As soon as you get your syllabus for your classes, put the assignments in your planner. When you're on the go, in class, or at home, you can look in your planner as see when stuff is due. Once you're done copying your syllabus' into your planner, tape the assignments lists to your desk, your notebook/binder, or anywhere else you will frequently see them. As you go along in the school year you will easily be able to mark off what your have done and focus on important dates.
7. Clean your computer
Organize your files, delete old stuff that you will never need, and have all your bookmarks ready to go. Nothing is worse than not being able to find an important file and having to click through a ton of different folders to find it.
8. Determine when you're going to wake up and go to bed.
For me this year it was easy to determine that I need to get up at 7 a.m. every weekday morning because I either work or have class at 8:30 a.m. As tempting as it is to sleep in every day until the last minute, I know that I need to have an hour to get ready and 30 minutes to eat breakfast, so I trained myself a week before classes started to wake up early. Also try to determine a time when you will be in bed by figuring out when you plan to do most of your studying/sports/activities. Try to aim for at least 6-8 hours of sleep a night.
9. Set the days when you will do errands
Find the one day a week that is set for laundry, dishes, room cleaning, errands, paying bills, and whatever else you need to do. Trying to find random times during the day to do things can make you feel stressed and rushed, but dedicating a day to run errands helps you manage your priorities and time better.
10. Pre-schedule your readings
Despite what some may say, doing the readings before class is better than winging the discussion in class because you're actually prepared. Look at the chapter(s) you have to read and schedule a time to go to the library or a quiet place to read; you could end up trying to read a 50 page chapter at 10:30 p.m. for an 8 a.m class, or you could end up only needing an hour minutes for 50 pages that you know has a bunch of pictures and diagrams rather than heavy reading. By scanning your readings, you can save yourself some time and a lot of stress.
11. Schedule relaxation
That can sound dumb and almost seem like you're micro-managing your life, but it will save you so much stress in the long run. By scheduling your relaxation time you're more likely to actually relax because you know you have managed your time well enough not to worry about relaxing too long or procrastinating.