Don’t worry too much about what people think of you; you’ll over-analyze the situation and they might judge you for that. Be genuine and be nice to everyone, no matter how mean they may appear at first. It’s usually always the ‘girl/guy that you hated at your new school’ that ends up being your friend after a little sincerity. Don’t be afraid to stand up for yourself, if it’s very clear that you should.
Asking for directions to a class, for example, is a good way to talk to people and meet a lot of people on your first day. You’re the new kid now. Mention that to people whenever you need some help.
Be nice, and optimistic, even if there happens to be an annoyance. They might even let you be the annoyance to another new kid someday, it usually takes a year and a half, but they’ll come around. Always remember to make a good first impression but it’s also important to be yourself.
It can be the most tricky, manipulative people that talk to you at first, and it’s usually those who just talk to you later on, at the back of the classroom who are there for you later on.
If they accuse you of something you didn’t do, reply by saying you’ve never done whatever it is they are accusing you of, and then ask them who had said that.