[edit] Steps

Be shy, but not too shy, let him know you're into him before you ask but don't charge up to him and demand. Guys love girls when they first come on to them, and they're kind of shy. Laugh at his jokes, and ask questions about him.
Then casually ask if he is going to homecoming. If he says yes, then he probably has a date already. If he says no, them go for it!
If no just ask him! like " me and some friends are all going together would you like to come with me?"

[edit] Tips

Try to be yourself.
If he is a shy person, initiate the conversation. If he’s not a really shy person, then let him talk.
Be the one who has to leave. Make him want more. Stuff like, "Oh, I have to go, but I'll talk to you later" works really well. That way, he doesn’t think you're obsessed with him.
If he’s busy, ask him to call you back. Don’t offer to call him back.