How to make NEW friends at an OLD school?

How do you make NEW friends at an OLD school? I'm shy and I don't have very many friends at school, just aquantiences I can say 'hi' to, no one I can hang out with OUTSIDE of school. I really want to break out of my shell and join a new friendship group but I don't know which friendship group to choose and i'm not sure how to shake off my old reputation of being quiet and shy. I want to be myself, because around the few close friends that I have (all at different schools) i'm chatty and funny .I suppose i am scared of what people will think of my new change, and what the people who I try to to make friends with will think of me. Help! So confused.