Some creative ways of asking someone out include using baked goods. Write a message around the cookies, brownies or whatever baked good you have chosen to use. Another idea would be to use quotations or a romantic poem. Find more suggestions from the following site http://www.tipjunkie.com/favorites/how-to-ask/.
give them a bunch of riddles. start by leaving one in her locker that leads her to your car, to you house, and in the end to your kitchen which says "Will you go out with me?" spelled in roses or something. (suggestion: make the riddles obvious so she/he knows where to go and not get lost. xD