Sell nicknacks with an ebay account. Because of your age, you'll want to do this with a parent/guardian. Alternatively, you could register with a Google Adsense account (also requires a parent/guardian due to your age) and advertise on any youtube videos you have/will make.
You can also use Adfly to shorten URLs and gain profit from people watching 5 second ads, though that will also require parental supervision.