The late, great teacher Davis Love Jr. had a saying: "You have a contrived set-up so you can make a free swing; a free set-up leads to a contrived swing." That's why, despite what I said in Rule 1 about the swing, positions have their place -- in the set-up.
A common mistake is pointing your toeline at the target, which produces a closed stance. Your feet should be aligned parallel to the line that runs from the ball to the target. To envision this, stand behind the ball and extend both arms parallel in front of you (large photo). Point the right arm through the ball and at your target; this indicates the target line. The left arm indicates your stance line, which extends left of the target. Next, rest a club along your right arm (inset photo) to ingrain the image that only the clubface touches the target line.