Before you ask a girl out to homecoming, it's important to understand what the girl in question likes. For instance, if the girl is shy and you start out by making grand gestures, it's just not going to work out. Figure out what the girl likes and start off your proposal based on that. You're not only trying to get her attention before you pop the question, you have to let her know that you care. You have to let her know that this isn't just a fling and that proposal means a lot to you.
Make her feel wanted. Don't make the girl feel like one option among a dozen other ones.