I was 17. Freshman at college. The bass player in the band I played guitar in.
Here's how it started:
We were practicing in a dark abandoned bookstore and she was standing in an area of relative lightness. I didn't know the songs very well so I was watching her hands on the neck of the bass to sort of follow along. She thought I was checking her out. So she seduced me over a bean and cheese burrito in the seedy tavern on campus.
It turned out she was also sleeping with the lead singer for the first week or so of our relationship.
I was 14, on my mom's walk in closet floor. My gf had to have it in the dark, and it was the middle of the day. Needless to say the sex sucked. First time for both of us.