Break students up into groups. Have them use one cell phone or have flip cameras available for them to use. They each get a different version, with the same clues just in different order so they aren't all going to the same place at same time. First three groups back win. Prizes can include a free day of not dressing out, a free homework pass for health, etc. This has a lot of clues of items that you can find around a typical high school. May have to tailor to your specific school.