Basically, in tennis, you want to strive (as much as possible) to hit each ball the same way. So, with a low ball (how low?) you want to get to the ball in plenty of time to set up- and since the ball is low, you want to bend your knees and get down low, yourself, so you stroke will look and feel much the same as hitting a ball in your comfort zone.
Concentrate on the racket path you need to direct the ball to where you want, then drive through the ball with enough low-to-high motion to generate topspin so you get the ball over the net-- then back down into the opponent's court.
For this sort of thing, practice is the key. Have a friend toss you some low, mid-court balls. Practice getting down and hitting through them firmly and fluidly-- through the ball and low-to-high. Pay attention to the result and adjust as necessary until it becomes second-nature.