I must have got a real early start, I was kissing a girl friend at age nine. But I got into the more passionate and what you might call 'fore play' stuff - which I admit got me nowhere - at fourteen. At seventeen teens used to form liaisons for this sort of thing in the movie theatres. The girls were every bit as willing as the boys and it didn't seem to be held to much against us if we changed partners every now and again. And I expect the only reason it was so hard to get girls to 'go all the way' is because this was way, way before the advent of the oral contraceptive pill.
Later it was the Saturday night dances where one would pick up a girl with the hope of...well...but there was usually plenty of kissing and fondly going on if not what we boys were obviously pursuing.