I saw a few guys I like do this on Google+, so why not?
I've posted about this before, but here it is again.
My first RPG was back in 1981. To keep it short, I'd seen my uncle's D&D books and I was fascinated by them. I convinced my mom to get me the D&D Basic Set for Christmas.
A couple of kids of a person she knew played the game, so they got to babysit me one morning and run me through B1 The Keep on the Borderlands. The older brother originally wanted to run me through his own adventure, but his mom told him to show me how to play with the game I brought - for which I'm eternally grateful.
My elf, Goldleaf, and the DM's brother went up to the gnoll caves and inside. I'd read the module but couldn't figure out how to match the maps to the text key. We fought some gnolls, ran from more, and eventually ended up in the chief's room. There we blocked the door behind us and killed the chief.
After that, we found our way to the wight, shot him up with some silver arrows to no avail, and then ran.
I made it back, the DM showed me how to read the map key and match it to the text, and I was off.
Those guys also owned the DMG (which I was fascinated by) and the Fiend Folio, which mesmerized me to the point that I bought it as soon as I could - before the Monster Manual, even.
I owe my first misunderstandings of D&D to those guys, too. They played AD&D, and converted me on the spot from a D&D Basic Elf to a F/M-U/T, and had me roll for spells known. They told me I could cast each one once at 1st level, and I did. They also let me keep my HP roll from being an elf, which led to a total and systematic misunderstanding by me about how multi-class HP worked, too.
But all in all, they taught me to play. I'd later play in my uncle's game, too - same guy I gave the PHB back to not all that long ago.
And naturally, I incorporated this experience into my current DF game!