Do not lift your head/eyes during your forward swing to look at your target area. The temptation is great, but moving the head to look at the intended target area will usually throw off the swing path of your racket resulting in mishits. Instead, visualize
your target area and keep your head very still during your forward swing with your eyes trained on your contact zone. You can look up as you are finishing your follow-thru. Federer and Nadal provide very good examples of keeping the head still and the eyes "quiet" during their fwd swing.
Originally Posted by Cheetah
Hit the inside of the ball.
Hitting the inside of the ball is fine if the OP can do so w/o hitting the ball into the alley (within the tramlines). However, the IO Fh can still be executed effectively (and more safely) hitting on the outside of the ball instead.