If memory serves correctly, I first played a scout camp when I was 12, in the summer of 1983. I then found a red box basic set at a garage sale, and started to play with my next door neighbour, and introduced some friends from school to the game. I then found a blue expert box set and we used that too.
One day my neighbour showed up with a hardcover Player's Handbook. Once we found out about the concept of a game store where we could buy all sorts of neat things to do with the game, we were in trouble... It has been that way ever since - I'm still gaming with one of my original gaming group!