BOY ADVICE: please help me on what 2 say?

there is a boy that i like and he's n high school and im in middle school. he goes 2 the school ill b going to nxt year. i only no him because ive had a tour and my friend who goes there told me a liitle about him. so i want 2 fb message him BUT i have no clue what to say because we haven't met..he has just seen me.... =/ i don't wanna seem lke a stalker..