An important key to a good forehand is the shoulder rotation. As a beginner, it's important to stress the shoulder rotation. I've found when my forehand starts to go astray, if I concentrate on this tip I see imidiate improvements. When setting up for a forehand I start with my chin touching my front shoulder (as a right hander this would be the left shoulder), swing through until my chin touches my back (right) shoulder. As I swing the head stays relatively still and the shoulders should rotate through the hitting area.

With this Andre Agassi's forehand (Circa 1995) you can see this in action. Notice the full rotation of the torso. His arm just follows the path of the his right shoulder, and the racquet head is .