Ignore everyone else's advice for now, and listen to mine. Your first priority should be getting acquainted with the school. Go to all your classes, find your way around the place, get your schedule memorized, etc. If you do that, you'll do fine. Social interaction comes next. After you've gotten comfortable, try to make some friends. There are two important things to remember here: 1. Be yourself. 2. Don't try to make friends at lunch. Why the second one? Here's why: At lunch, people prefer to eat with people they already know. If you, the new kid, come up to a table and just sit down, there's a good chance everyone at that table is going to get up and leave. Wait until you've made some friends, then sit with them. Also, it's helpful to have some sort of interesting (but not annoying/irritating) quirk or physical feature. For example, people practically worship me because of my glorious sideburns (if you don't have sideburns already, don't try to grow them, as you might hurt yourself), and they all think I'm cool because I'm a furry (which was the last reaction I expected, but I don't have a problem with it). If you don't possess an interesting quirk or feature, then you are the only person in the world who doesn't. Don't try to imitate quirky behavior, though, as that's always obvious, and gets very annoying very quickly. Just be yourself. I can't possibly emphasize that enough. BE YOURSELF GOD FLAPJACKS DAMNIT!
Okay, now did anyone else give you similar advice? Good. Take their advice as well.