Dont be scared!!! i was just starting last year and i was so scared, then on my second day i was just like why the heck was i so scared! dont waste your time on it, hang with your friends the first day soon you will have even more! have fun :)
It's all about your education. Wear whatever you want to wear, but make sure if follows the school's guidelines and dress code. School's not a fashion show and not about boys. You can be friends with people, but make sure they are a positive influence. Don't socialize a lot. Don't get in any kind of trouble. Avoid drama. If anyone tries to bully you, just be strong. Hold your head up high, but don't get involved. Most importantly, be yourself.
I like what Exhausted_Love said, so I'll begin by restating it: "Don't get pregnant". Other than that, (don't get pregnant) it's pretty much like middle school (don't get pregnant) in most ways. Same people you were in middle school (don't get pregnant) with, same boring classes (don't get pregnant), same annoying (don't get pregnant) teachers... It's not too different, really. Basically, don't get pregnant.
BE YOURSELF. Don't worry about what people think of you as long as your acting like yourself.. Focus on your bestfriend and not a boyfriend at that age because boys will just get you in trouble.. & have fun freshman year was my favorite year enjoy that year because once you are in High School it's different...
Get involved. Seriously. Clubs, after school activites, sports..anything. When i was a freshman i regretted mot doing anything because it was my first year of high school. I go to fill out a collage app and it gives me spaces for what i did as a freshman. Nothing. Get involved!
Don't be afraid to be yourself! Kids can be mean, but when you "grow up" you'll wish you didn't spend so much time worrying about what others thought/did. What seems like major drama will seems trivial. Enjoy the next four years and study hard!