I was always basically a high-ball hitter, but late in my career I've been able to keep the ball down better -- in the wind, or playing a bounce-and-run approach into a green that's open in front. Keeping my left shoulder lower at address (1) and through the ball has made a big difference. If I keep my left shoulder lower, the ball will go lower.
I can move the ball back in my stance (2) and feel comfortable, where I couldn't before. I move it back to the center or farther for a low shot with a middle iron. (I square my clubface to the target when I do this.) I stand an inch or so closer to the ball for low and high shots, or I'd hit the ball off the toe. Finally, I finish lower (3).
An example of successful execution is a low 5-iron approach I hit to the 10th green in the British Open at Turnberry last year. It's a long par 4 with water on the left, and it was playing into the wind. I hit it to about 30 feet with a lower trajectory than normal so it rolled after it landed short of the green. I made a solid par to keep my round going.