I am seeing a consistent pattern of students who are not getting the most out of their irons. At the onset of every lesson I ask my students what are you trying to do in your swing? The responses I hear are not usually conducive to striking a good iron shot of the ground. So trying to stay behind the golf ball or keep your head down is some of those responses you should forget.
The key to compressing your irons is to understand where your body and club need to be at the moment of impact. If you look at any good player you will notice this player has more weight on their left side for a right handed golfer at the moment of impact. This means that the shaft of the golf club would have a slight lean in front of the golf ball. So this is where it becomes tricky. When you are making a backswing it is imperative that you do not shift to much weight or sway into your right side. It will make it extremely difficult to get back to a good impact position.
When you successfully get your body and club into the right position at impact you will notice a couple things. The sound of the golf ball coming of the face will be different. You will also be striking more ball first ground after with a divot after the ball and not before it.
Some drills the will help you get the feel of this position.
1) Set up to the golf ball with an 8-iron and draw your right foot back so 95 percent of weight is on left side only using your right foot for balance. This will help you feel where the body needs to be at impact.
2) Set an alignment rod 8 inches behind the ball. Hit some balls without hitting the alignment rod. This will help you get your weight more forward at impact so you can compress the ball.
Rico Riciputi, PGA