Read Your Wrists
The position of your hands at the top of the swing usually predicts the type of impact you'll make.
Hooked and pushed shots tend to come from an overly flat position, where the left wrist is bowed, the club shaft points to the left of target, and the clubface points straight up at the sky. Slices and pulls are the most common results of an upright position at the top, where the left wrist is cupped, the shaft points to the right of the target, and the face of the club is aligned almost vertical with the ground.
In the ideal position, the back of your left wrist should be on a straight line with your arm, and the club should point parallel to your target line. Your clubface will be in a square position, pointing roughly on a 45-degree angle toward the sky.
Photos and videotapes can show you which position you're in, or you can ask a friend to check you on the practice tee. The basic idea is to swing to a position in which your hands are directly above the top of your right shoulder. If you get them outside or below the shoulder you're too flat; if they get between the shoulder and your neck, you're too upright.