When I started, I was still in high school with. I didn't have a clue on how cars worked or how to fix this and that. I bought my own set of tools and then started doing basic maintenance on my parents cars like oil changes and minor tune-ups. Of course I've never done this type of stuff before so I did some research and just followed instructions. It was pretty straight forward but you do get to use your hands which is good.
After a while I started looking at the engine in more detail as in where is the head, block, oil pan, intake side, exhaust side...etc. etc...and I just think my way through. So I got more confidence to do more stuff as time passed since I had been doing alot of electrical and mechanical repairs and through that, I gained alot of insight on this stuff.
I also bought a motor for really cheap to rebuild. I got it for $100 so it was pretty cheap. I just look in the service manual for specs and just kept thinking my way through things. In the end I'm pretty satisfied where I am at right now..of course there's alot for me to learn but I do feel confident enough that I don't ever really need a mechanic anymore...except for some jobs that I dont' want to buy a tool for like pressing out wheel bearings.

get your hands dirty and do whatever you can...as someone suggested..be the tool monkey!