Your age does not matter. Depending on how old you are and if your a first time entrepreneur I suggest that you have a big vision but adjust your tangible goals correctly to the amount of time and resources you have available to you. Perhaps aim for something you could easily sell to another company or a product that can gain paying customers.
In terms of finding a co-founder, why not partnering up with another teen? Events like Young Rewired State (UK - http://rewiredstate.org/events/young-2010), hack days and barcamps all usually have teens attending them.
Check out TeensInTech (Bay Area - http://teensintech.com/) which also runs a teen tech incubator.
There are also a few online young entrepreneurial groups such as Millennium Generation https://www.facebook.com/groups/rockstars and theres WebeTalk IRC chat (http://webetalk.com) which is frequented by some of the youngest YC startup founders.
If you want to take a different more active approach try building something small and useful that will get you tons of press and coverage on HackerNews. You can also tip TechCrunch (tips@techcrunch.com), building something that people are aware of outside of you telling them will definitely help you find and secure a co-founder. On top of that the media and others absolutely love young entrepreneurs stories. So with a bit of work you will be able to get coverage.
If you want to team up with a more experienced person, why don't you ask them to be your mentor, ask their advice (it's generally good to have personal advisors, they'll help you out). Build that relationship and if things look good, maybe you could ask them to join as a co-founder or help out. Many startups do this to acquire higher level executives or even investors.
If you have a technical background, you don't need a co-founder to start. I hope this helps and good-luck, many of us have been there before.