Senior in Atmospheric Sciences here and hopefully moving on to gradschool. The most important thing to consider as an incoming freshman is to not let yourself get carried away. I really liked being able to live independently from my parents as well as having more free time (at first, anyway). But the fact that you have to make all of your own choices can also be a trap: For instance, you should always resist the urge to skip even just one class if you can. I also, like several others before me have pointed out, highly suggest finding something to do academically outside of your classes. In my case, it was getting involved in an area of research I was heavily interested in, and with that I have gained some motivation to work harder as my program has become more difficult.
One other piece of advice that I am surprised to not see mentioned at all yet: Learn to deal with your roomates well. Unfortunately, far too many of us likely had our hands held by our parents as far as chores or cleanliness would go before college. As a result, your roomate will probably be a big slob and likely so will you. If you really don't give a shit about keeping your place clean (though you should), then it probably won't be a problem, but I found it a bit tricky in my case. It isn't as applicable to dorms depending on their size but it can be a huge headache if you later move into an apartment. In general, it is best to start off by being courteous. If I constantly pressed my roomate to clean up the sink, he would just brush me off and call me a nag, but when I asked him to politely, he happily obliged. In an ideal world, you won't need to ask but unfortunately this will likely be the case.
