Whats the best way to win a pitch?

At school we are doing a competition to brainstorm the best teenagers product, which will be decided by the teachers, and then ( 100% serious ) pitched to Tesco. Our idea is a chunky baseball cap, with headphones and a mic that retract down from the hat, and a USB for plugging into your PS3, xbox, PC etc. How could we best use our idea to the max and create the best product to win the pitch? Eg, a detailed powerpoint or something. The prize is �50, and the money from Tescos orders ( if they take it )