I can't really prepare you.
People have very different adventures during their first year.
But most come away from freshman year happier, more mature people. Here are some pointers on how to deal with the major parts of your first year. I'm incredibly messy and do student government and debate. My roommate was 6 feet 2, played varsity football, and chewed Skoal. Either someone in the housing office had a sick sense of humor or one of us lied on his housing form.