Coming down, keep your left elbow pointing at your left hip.
Amateurs struggle with iron shots because they don't square the clubface to the target in time for impact. Why is this problem so prevalent? The left arm doesn't function properly. I'll explain.
If you just pull your left arm down from the top, as many golfers do, you have to do something else at the last millisecond to square the clubface—or it's Slice City. Instead, rotate your left forearm counterclockwise on the downswing.
A great thought is to keep your left elbow pointing at your left hip as you swing down (above). If the elbow points at the target, you're pulling, not rotating.
Get used to this left-arm rotation with half shots. Shorten your backswing, then rotate your left arm through. It'll feel as if you're directing the clubhead out toward the ball. You'll start striping it.
Mike Malaska is a Golf Digest 50 Best Teacher based in Mesa, Ariz.