How do I start my own nonprofit/volunteer program for teens?

When I was 13 I started my own teen volunteer group in my hometown. It was very successful and I was very good at organizing it and actually loved what I was doing. It's been more than 10 years now and I'm living in Austin TX. I would really like to start a legitimate volunteer teen outreach program to get kids involved with their community but don't know what steps I need to take to get this idea off the ground. Any suggestions?