The second part of this series ties in a bit with part I of the series.
This is the understanding that in order to hit the ball first and then take a divot, the golfer needs to hit down on the golf ball when using an iron. Furthermore, I would suggest golfers that are struggling with taking a divot properly with an iron should probably hit down with the driver as well until they can properly hit down with the irons.
What happens when a ball is properly compressed and a divot is properly taken is the clubhead comes to the ball at a downward angle. It then hits the ball and after it hits the ball the clubhead continues downward. This video is a shining example of it.
According to Trackman, the average attack angle for a Tour Pro with a 7-iron is about -4*. I've read about 30 different Trackman reports, and the mid handicapper's attack angle is closer to zero degrees or a 'flat' hit. It technically is possible to hit a good shot with a very slight upward attack angle with an iron. However, you won't be able to compress the ball properly.
The reason for this downward attack angle is due to what's called the 'low point' of the golf swing.
While this diagram is nowhere near being scientifically exact, it gives a ballpark idea of what the 'low point' is.
If you're looking at the golfer's swing from the Face On view, it appears the clubhead moves in a circle or an ellipse somewhat like the diagram above.
At the very bottom of the circle in the diagram, that is the lowest point the clubhead travels in the swing. That's what the 'low point' refers to.
The low point is also about somewhere around the left shoulder. Some efficient golf swings may have them a little bit in front or behind the left shoulder, but for the most part it's at about the left shoulder. So again, the lowest part of where the club travels is opposite of the left shoulder.
So what happens is most golfers have the ball position with the irons about about the middle of their stance. If they execute a pretty decent swing, they will hit the ball first because the clubhead still has a way to go before it reaches its lowest point. Then after the ball is struck, the clubhead still has a way to go before it reaches the 'low point' and thus the clubhead has continue moving downward.
The problem most golfers have, including professional golfers, is that they tend to have flaws in the swing that cause the low point to move around. Sometimes they'll get the low point near where it should be and they'll hit it flush. Sometimes they'll wind up moving the low point too far forward and hitting it thin. Sometimes they'll move the low point too far back and hit it fat.
If you look at professional golfers' Trackman reports and even good amateur players, their attack angles are not only steeper, but more consistent. A PGA Tour player who has an average attack angle of -4* with a 7-iron will likely not see much variance in that attack angle even if they recorded 100 shots. OTOH, the higher handicapper will likely have a shallower attack angle and the attack angle numbers will vary by more than 1*.
One tip I suggest for understanding how to hit far enough down on the ball is to go on the range and step on your golf ball in order to plug the ball into the ground. Then try take your normal golf swing, but attempt to get the ball flying in the air the best you can. You should inevitably understand that in order to get the ball flying in the air, your only hope is to hit down on the ball. Hit a few shots trying to do that, even if you don't hit a good shot. Afterwards, give yourself a 'normal' lie and just try to hit down on the ball like you did when it plugged. You'll eventually start to get the sensation of what it's like to hit down on the ball enough.
Also, if you can get out 9-holes of golf, play what I call 'reversed winter rules.' Instead of improving your lies in the fairways or the rough, seek out a divot and place the ball in the divot. You will find that in order to hit that ball out of the divot you need hit down on the ball.
You can also get some time on Trackman and tinker around a bit until you get the proper downward attack angle.
Lastly, there's also Martin Chuck's (Richie3Jack Golf Blog follower) fabulous 'Tour Striker' training aid which is specifically designed to make the golfer hit down steep enough.