This is an easy situation considering you go to the same school. Like ELITE said just go up to her and say "hey, how you doing?" ask her if shes liking the new school, what subjects shes taking. Keep the conversation short, so then next time you see her, you can say "hey" more comfortably. Let her know that your a nice guy the first time you introduce yourself, dont talk to her while tihnking how hot she is. Just talk to her as if you have no attraction watsoever (helps with the nerves).
Also do not stutter when you speak to her :thumbsup: