The key thing at staying low and the difficult part for the player to remember is to start low and stay low. Many players will be low in the ready position but raise up to advance on the ball to their left or right. They will stand up to run then try to get low again, often this results in "stabbing" at the ball. Try to work on playing the whole game 6" lower. Stay down, you will be quicker then getting up to go and then getting down to field.