Social help. How to talk to girls?

I have tons of friends that are girls. Never had a girl friend. And I don't have any of their numbers. I'm kind of the shy kid, but in school we talk a lot. I've thought about asking one of them out, but I'm too nervous. I don't know what to do. I really don't even know how to get her number. Because we really haven't talked much this year but we've known each other since we were like 7. Help please.