I recently did a lesson where the player asked why his forehand was so inconsistent. After feeding him 6 balls the answer was obvious. He played a different shot with each ball. Not that he was trying to play a different shot. But each shot was different because the contact point was wildly different. So imagine there is a bubble just to the side of you, slightly in front and around waist high. Now see if you can make contact with the ball within that imaginary bubble. This means moving your feet and getting in the position. The size of the bubble will largely depend on your ability but the smaller you can make it the better.