Follow-through :

The follow-trough is also an aspect of the swing that can be a problem for some golfers. Most people first held a baseball bat or a hockey stick before holding for the first time a golf club. The fact that a baseball or hockey swing is a natural for some golfers will cause a bad follow-through. Many have the habit of turning the shoulders and upper body too quickly after impact instead of letting go the arm extended toward the target. This will cause a shot to the left for the right-handed golfer and a shot to the right for the left handed golfer.

Here is an example of a problematic follow-through. Note where the club comes out after impact. It should come out on top of the shoulder. In this picture the club is out too much to the left causing a missed shot to the left. Look at the red items, they indicate the position of the ball and the club, while the green items are the corrections that should be done.

Here is the same swing a second later. You can see the club too quickly to the left of the golfer. Look at the direction of the ball.                 

                     Now comes a nice follow-through