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
On the course you should focus on simple thoughts when you swing, generally keeping to one thought per round but rotating through them each round
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