An important factor in getting the body into position for a great impact is the manner in which the shoulders pivot. Far too many golfers are trying to turn too much and get their lead shoulder behind the ball.
When the left arm is parallel to the ground (for a right hander), the right forearm is always slightly above it (when viewing from an image captured at waist height). I found this to be true for all of golf's best. In some cases the right arm is against the side (Hogan, Snead) and in others it is away from the side (Nicklaus, Norman), yet due to the method in which the shoulders were pivoted, the right was always above the left.
It is vital for the shoulders to pivot on a relatively steep plane.
Notice Nick Price's right forearm and how it is comfortably above the left. This is all accomplished by pivoting the shoulders on a fairly steep plane. The higher the right shoulder, the higher the right forearm and so on...
In a correct pivot, the left shoulder’s first move is down and then slightly across. This is in direct contrast to what most golfers attempt to do with their shoulders, which is:
a. turn them as much as they can and
b.get the left shoulder behind the ball.
Very seldom do any of the top golfers get their lead shoulder very far behind the ball(notice Price's lead shoulder!) when pivoting into the backswing(with an iron); an interesting observation when considering the fact that there should be little to no lateral movement with the head and upper body.
A point of interest: the best ball strikers tend to move off the ball very, very little (Faldo, Price, Hogan), and the golfers who relied more on heart and amazing short-game ability (Player, Ballesteros) tend to move off the ball slightly.
The fact that there is little to no lateral movement with the upper body seems to encourage the shoulders to work on that steeper plane.