Anyway, as for meeting girls, as others have said smiling and waving are probably your best bets. You're not getting out of school tomorrow or the next day or even soon- you have plenty of time to meet her. Let the opportunity present itself and then work with it, and interact with her when you have the best chance. As long as you don't look creepy or actively try to stalk her I'm sure she will be flattered in some way. Even if you don't instantly get a date (which you shouldn't, friends first is -always- best), you will flatter her, and if she's not already taken and not a prick who only cares about appearances she will consider you. This is coming from a girl herself, guys.
If you want me to tell you how I met Sudai, I can, but I'm not like 90% of girls (especially most younger than me) so it's not gonna be a typical thing at all. I wouldn't recommend asking me, you might end up using this advice on the wrong girl (which would be most of them).