Pretty much what Frasbee said. Just start talking to her someday.
Be like "Hey baby. Whats crackin?" (Or, insert random greeting. One day you will find one that fits your personality.)
Chicks dig a guy who tells it like it is and isn't afraid to walk up to them and say "Whatsup?"
Or, if MSN is your thng, ask her to meet you sometime or somewhere for lunch/diner/coffee. This will help to eliminate the "scary" aspect of school and being around "friends".
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