EASY IRON MOVE 3: KEEP YOUR RIGHT SHOULDER UP
Just as I want to feel taller at address, I want to feel taller as I make my downswing and move through impact. I focus on my shoulders -- once I start turning them I don't want to raise them or drop them closer to the ground. I think of it as a "level turn." My big error is dropping toward the ball, or dipping my left or right shoulder. Now, a lot of great golfers make this move and hit incredible shots, but for me, it's a killer.
Once you start to turn through the ball, picture a dot in the middle of your chest, and keep that dot moving toward the ball on a straight line. Feel like you're swinging more "around" your body. (Your arms will take care of the "down" part.) If you do it correctly, your swing will feel flatter, and for most slicers this will do wonders for your ball flight.
TRANSLATION: MATCH YOUR TURN TO YOUR SWING
Sergio's "level turn" actually happens on an angle, but it's more level than what you typically see on Tour. As important as it is to his swing, most people miss it. Because he drops to such a low plane on the way down, making anything but a level turn would cause Sergio's swing to move too much out to the right and shift the bottom of his arc behind the ball. In other words, if he had practiced making a steep turn rather than a level one growing up, you never would have heard of him.
Steep swingers (those who swing down on a more upright plane), need to move their right shoulder down to keep the club from getting too far out in front. (Jack Nicklaus is a great example of this type of swing.) The flatter your plane, however, the flatter you should turn through the ball.