Like a few others I have been mucking around with the ball position recently - just trying to find a way to make it simple on course. When I practice I often use alignment rods and it makes the process pretty simple. I go with the club head off the left heel approach recommended by Tom. On course it is not as simple for some reason so I worked out a method that seems to make it a lot easier for my brain to understand.
I start with a comfortable shoulder width stance and put the pall in the middle. When I stand over the ball my brain can feel the ball is indeed centered and I tested this many times using the alignment rods. Form there when I put some weight on my left side the ball position shifts to my right eye - again I can feel this very consistently, and my club path low point is just ahead of the ball. Then I just keep my left foot in place and move my right back, depending on what club I have in my hand, to get the balance and power position I want.
With this method it makes it easier for me to consistently move the ball forward or back in my stance if I want to move the ball at all - which I am learning to do. This works for pretty much all clubs with the exception of the driver which I still prefer to have more forward. It just feels right and keeps me from hitting the ball to much on the heel.
AE
Interesting discussion because Nicklaus maintained a constant ball position (or so he illustrated in his books), meaning he aligned the ball to the inside of his lead heel. After that he adjusted his trail foot forward or back pending the length of the club. I'm sure he actually did move the ball around, but in the grand scheme of things it makes sense to position the ball at the low point, which is (more or less) slightly to the right of the lead armpit. Moving the ball around is fine, but IMO one should only do so after one can consistently hit the low point.