How do you get a girl alone to ask her out?

Ask if you can talk to her for a minute and find someplace with hardly any people. That's probably the best way, since you probably won't find many times where you are alone together by coincidence, and you need to make sure you're ready (mentally) to take the step of asking her out at that moment.

Okay, thank you, but the best place i think that i could ask her would be in the courtyard after lunch, but she never comes out. She always stays in and talks to her friends.But ill figure that one out on my own.

Thanks for the help!

no problem.
you might not be able to get her TOTALLY alone, but if you're somewhere where nobody can hear you, but there are still people around, like maybe in a quiet corner of the cafeteria that might work...............