Another thing is just finding something you have in common to talk about. And although I don't recommend doing this if you think it'll get you in trouble with your teacher or distract you from class, taking part in the side discussions that go on in class actually helps. I say this from experience. Don't like go overboard talking in class but when people around you are you can join in.
Just don't be scared to speak up and think of everyone as a friend. People you have a couple classes with, stop and talk about the coursework, the teacher, someone else in that class. It's really easy to find things to talk about when you start trying. Also a good way to find people who are actually like into the same things as you and you can probably get along with better are by joining clubs.
Hope that helped.