Just focus on your studies. And don't worry about the others. You're future is more important than they are.
Can anyone give me some good advice for my first year of High School??
I started high school when I was turning 13 because we start high school in grade 8 in Australia (saying this, however, the laws have since changed and high school starts in grade 7 now), and socially, it is important to make close and good friendships. Nothing fake, or you will start stressing and making other people stressed (my friends have been known to do this). Nonetheless, as you get into you get into your sophomore years and beyond, your grades start getting more important, so you should keep them up as well. :-)
Have you seen the movie - 21 jumpstreet? Channing Tatum says it all.
(Serious) - just don't think about it. Worrying makes it way worse than it is. I recently finished, only problem I had was where to sit at lunch on the 1st day lol