My dad mostly, but when I came upon car-specific forums I got a little braver, and decided to try more in-depth stuff. From there on out I've taught myself a lot through reading and doing. It helps a lot to have a bigass database of everybody else's successes/failures, and how they did it/fixed it . Like I said my dad got me started with just oil changes, brake jobs, tune-ups, etc., but now I know quite a bit more than he does.
I've done some things with my Stealth that nobody else had done before, and a few have now tried some of it with the help of my walkthroughs... I've come a long way.