Girls, PLZ HELPPP!!!!!!!!! I do not know how to do what i want to do, PLZ HELP!!!:)?

I really like this girl, and i mean REALLY. I've known her since grade 8, and know we are in grade 12. I am really shy, but this time i am going to go straight up to her and tell her i think shes the most beutiful girl i ever saw and that i would like to get to know her better or something. Thats the thing, i dont know if i should say that and what else. I have genuine feelings for her and im scared of what her reaction will be. In graed 8, during the summer, i was being a and told her on msn i liked her but only because i was gullible and took advice from the wrong fags. I didnt see her from grd 9-11, only like a few times. Now shes in my cl, we've started to talk more, and on thursday we were laughing with each other because we were telling inappropriate blonde jokes, and shes blonde but she was relaly laughing, which made me feel good knowing she didnt take them the bad way. Know, i keep thinking about her and i want to get to know her better, but i seriosuly dont know ...