It all starts with confidence. Try talking to some random person in the hallway or class each day, and become friends with them. If they are part of a clique, you will soon become friends with the clique. Do this with each group (Dont forget about the other groups!) and youll be the most popular kid in school, like me ;D
It's better for people to like you as you. Don't try to be some1 your not. You are unique and special and don't forget that. I'm not popular and I don't care cause it doesn't matter. You shouldn't care either, popularity is dumb!