J.D. Cuban
My left shoulder is under my chin, and my left arm is fairly straight.
Column courtesy of Golf Digest
Set the club short of parallel at the top of your swing.
I'm a proponent of a full shoulder turn -- one of the key sources of power in the swing and necessary for crisp, consistent iron play. It should be accompanied, however, by a proper setting of the club at the top of the backswing.
Some amateurs, when they try to achieve a full shoulder turn, take the club back too far. The shaft drops past parallel, which can compromise timing, clubface position at impact and power.
I allow the club to set naturally at the top of my backswing (right) so the shaft is just short of parallel. Then all I have to do is unleash my stored power on the downswing by rotating through the shot. This thought keeps my swing simple and repeatable.