How can I start making new friends?

[H B]

In grades 9 and 10 i fell in with the wrong crowd and got involved in some pretty bad things. This year in grade 11, i feel like I am starting all over again. I only have two friends in the whole school, and i feel pretty isolated and alone. I want to make friends with new people, but I don't know how to go about doing it. Does anyone have any suggestions on how I can deal with this and make new friends in my new classes?
I'm also a shy person, and I think that everyone has come to know me as that, and everyone has therefore decided that maybe the reason why I'm shy is because I don't WANT to be friends with anyone. But this is not the case. How can i break that perception of myself that other people have?