Are you a wristy player? If so it might be worth some effort training a new technique with a wrist assist, just a band wrapped around your arm. See the video about the wrist assist on this page http://www.tennisattack.com/social-player/
I find the wrist assist really helpful.
The ultimate tennis game:
Rafas T/S forehand
Djocos flat laserbeam shot
Gasquets T/S backhand
Rafas work ethic and nerve
Federers angled slice chip shots