Step 12: Teach People To Do Stuff
Folks at school would probably pay you to teach them to play an instrument if you're really good at it. Put up a flyer on the school bulletin board. If you're great at playing jazz, say you're giving "jazz drum lessons" or "jazz guitar lessons" or "jazz sax lessons", whatever you play. Same with speed metal, or any other any other genre.
You can take out an ad in the newspaper or on your local craigslist too, but make sure that it's clear that you and your gear will be going to their place, not a whole bunch of strangers to your place. Your parents probably wouldn't be keen on that. Big instruments like drums or piano should already be at their house (bring your own sticks), but something like guitar or sax is something you should bring for yourself. Don't bring one for them.
Offering the first lesson free is a good way to bring people in.
Keep a spreadsheet, whatever you do.