One of the worst clichés I hear is that you've got to keep your head down during the backswing. Too much of that (above, left) leads to the shoulder bouncing off the chin, and a shoulder tilt instead of a good shoulder turn (above, right). The same is true through impact. Too much focus on keeping your head down prevents you from turning through the right way. Your timing will be messed up, and you'll probably hit the shot fat. Let your eyes follow the clubhead as it hits the ball and moves into the follow-through. In other words, synchronize the swing of the club with the turn of your head toward the target. You'll start hitting it more solidly and consistently.
Avoid the tees for square contact
Few things are more frustrating than hitting the ball off center. It leads to inconsistent shot shape, trajectory and distanceand that's a tough way to play the game. Even choosing a club becomes a real challenge. If you're having trouble finding the middle of the clubface, practice with two tees stuck in the ground with the ball in between. Miss the tees, and you'll immediately start making flush, solid contact.
POSTURE (left): At address, bend so your arms hang straight. Flex your knees, and feel your weight on the balls of your feet.
STABILITY (right): Feel as if your feet are fastened to the ground. If someone pushed you from any direction, you wouldn't fall.