How can i get to hang out with a girl?

I like this girl and in a previous question i was told to try to hang out with her. she's usually with a friend and i can't tell her how i feel in front of her friend (that person spreads rumors all the time). I can't even work up the courage to say ';can i talk to u in private'; or something but i'm not afraid of rejection. i only see her at school and we're a little too young to go out. God! i need help!How can i get to hang out with a girl?
find somthing to show her. a magazine story ,a joke you found. and say hey can you come here for a min. i want to show you something. then when you show her say something like yeah i was reading this and i thought you would like it. if its a joke and she laughs that a good sign.