What worked for me:
1 - Buy an old car that needs work (starting with a '62 Sprite when I was 16, with many more in the intervening 27 years).
2 - Ask your Dad to help you fix it because as soon as I got it home it died and fluids started leaking out of it all over the driveway. My Dad drove me to the auto parts store, instructed me to buy the shop manual for the car, then drove me home and went back inside to drink beer and watch football. He did say that I could use his tools as long as I cleaned and put them away daily, although depending on your relationship with your Dad, you may have to buy your own shop manual and basic tools. I'll repeat jimeditorial's admonition about cheap tools because it will save you a lot of grief; I think that Craftsman stuff from Sears is a good minimum standard for the amateur enthusiast.
3 - Start fixing/breaking stuff using the directions in the shop manual. Mechanically inclined relatives or friends can help explain stuff in the manual that you don't understand, but use that lifeline sparingly as it will wear thin from overuse.
4 - Use antisieze; that way when you have to take it back apart to fix it again, there will be less breaking stuff, bleeding, and swearing. Antisieze is some very good stuff.
5 - And finally, borrowing from Bill Watterson; Memorize the following list of profanities, and learn how to use them appropriately:
*List available on request, not sure what the policy is on NWS links is on this forum*
Everybody grab your brooms, it's shenanigans!