The differnece between a low and high chip trajectory is simply the clubface on the backswing, keep it hooded to hit it low, open it up a little to hit it higher
It is critical to feel the weight of the clubhead throughout the swing, and this is accomplished by creating an awareness about the weight of the clubhead
There are three main reasons for the fat shot which cause you to impact the ground behind the ball resulting in poor impact and a short dribbler right in front of you