Having had no lessons, I remember the day I discovered topspin. I was hitting forehands that my Dad fed to me from a box. I was 11 or 12. After imparting it and watching the ball dip downward, I excitedly yelled, "Did you see that?!"
My Dad was learning tennis at the same time I was. He didn't notice.
Needless to say, I started using it regularly.
Up your backhand.