A few things I wish I had known going into college:
1) Buy books on Amazon used, then sell them back on Amazon used. 9/10 you will get the same price you paid for.
2) Find a group of friends that takes their week days seriously but enjoy their weekends. If their weekdays look like weekends, avoid.
3) Keep your door open at all times. If you have Mario Kart, play it loud enough people can hear. They will come.
4) Never, ever worry about girls. If you focus on yourself, your school work, your fitness/nutrition, your mental well-being they will take note and come to you (doesn't mean be a ****** bag and tell every girl off, just don't worry about pursuing anyone until you know with 100% certainty they are worth it)
5) Work with your advisor to really come up with a good four year plan. When you take the class is important, and there are ways to set up your schedule to take all the same courses in a much easier order.
6) Don't feel bad if you don't know what you want to do with your life.
7) If you want to study abroad, figure out all the requirements and information NOW or it could be really hard to make it happen.
8) Treat school like on-the-job training. You are paying for it, make it worth it.