Football coaches, how can I get into coaching as a young guy?

I wasn't a star in high school. I'm only 18, but I really have a pion for the game and like the intellectual side of the sport. I know a couple of my former coaches that might be able to help me out, but I wanted to know what the best way to get into coaching is and what I would need to know how to do if I was given a chance to help out. I can volunteer at any time and I can spend a lot of time studying the game. I would prefer to help break down film, but with no experience, I don't know if anyone would let me help with this. I'm pretty smart, so I think I would be pretty good at it. Plus, I know how to identify defenses. Anyways, I just need some advice. If I decide to go into coaching as a career, I eventually want to end up at a 4-year college, if that helps refine your answer. I'm willing to do anything to garner experience and learn the ways of coaching. Thanks.