Good for you for getting started so young!
I guess I have a different perspective on sticking with one airline than an earlier post. I think there's a lot of benefit to moving up the ranks of the loyalty program, but it's important to pick an airline based on its routes in terms of your location and desired destinations, as well as the strength of its airline alliance.
Happy to share my tipsheet on getting started. You can find it at
http://www.scribd.com/doc/17745143/F...Flier-Tipsheet.
If you have any questions, be in touch. Good luck!