One of the biggest culprits I see with a lot of students' swings is the head dropping down too much on the backswing. There are two main reasons for this. One is when the player is focused too much on trying to keep the head still and the other is caused when the left shoulder moves down instead of across when rotating it under the chin.
The effect of dropping the head is that the head will tend to lift up during impact as a compensation. As mentioned in previous articles whatever happens in the backswing will tend to be compensated on the downswing. When lifting up during impact it gives us a very small margin of error when trying to hit a good shot. The most common shot resulting from lifting the head is the 'top' shot. The worst result will be when trying to hit a fairway wood approach.
The correct motion of the head is actually the exact opposite. We want the head to be staying quite level on the backswing and on the downswing, the head dropping down a little. You will see this pattern with all elite strikers. The reason for the head to drop down a little is that we want to feel that we are striking into the grass on the downswing so that we get full compression of the clubface. There are examples though such as Justin Thomas who does drop his head on the backswing but keeps his down still during the impact area which doesn't compromise his ability to strike the ball.
Once you've identified that you may have this issue, there is a great drill which will ensure that you keep your head higher on the backswing. When on the range, find a range matt with a high tee. You want to place a ball on the tee and set-up with a SW, hovering the club just below the bottom of the ball. Your goal is to hit balls off cleanly without hitting under the ball too much. The more you keep your head up and on the same level, the more you will have success. If the head drops down, you will hit under the ball and most likely go a very shot distance. The SW is a great club to use for this at it's the hardest club to use off a high tee.
If you have any questions about stabilising your head just let me know and we can make a plan to fix this issue.