My dad had "the talk" with me one day when I was about 13 or 14: he was cutting my hair (being the Marine that he was) in the garage:
Him: "Uh, I suppose you've noticed that there is a difference between boys and girls..."
Him: "Uh, good."
A few days later I came home from school to find a series of books laying on my bed, "The Life Cycle Library." Kind of an "As We Mature" book of things to expect during puberty. It was a little late.