Think hit the lower outside of the ball and pull the racket head up, thru and across toward the CC corner before it wraps into your followthru. Visualize dividing the ball into 4 quadrants: Upper R, Upper L, Lower R, and Lower L. A right handed tennis player hitting a topspin CC forehand wants to think of hitting the lower R quadrant (lower outside of ball) and pulling the racket head up and across toward the CC corner from there.
In reality, if you use a slightly closed racket face for topspin as you should, the first contact between racket and ball will be on the outside of the ball but it may not really be on the lower outside. Think about it - it is hard (maybe impossible) to really contact the lower half of the ball if your strings are slightly closed. But, it is still a good visualization technique.
Last edited by TennisCJC; 11-08-2012 at 11:47 AM.