Correct Golf Ball Position
The position, or placement, of a golf ball in a player's stance is incredibly important to shot success. The problem is, it's also sort of vague. As a result, most amateur golfers lack consistency in their ball placement, leading to inconsistent ball striking.
One time they might hit a 4-iron with the ball near the middle of their stance and it didn't work, so the next time they move it up closer to the front foot. The change from shot-to-shot actually leads to more inconsistency and frustration. A player who does this, even subconsciously, doesn't allow muscle memory to develop.
That's another issue, this drifting from front to middle to back is often done without knowing it. If there were a yardstick between your feet to mark the ball position every time, that would lead to more consistency, but that's not an option.
Instead, we need to make it simple to remember and simple to repeat. So, we're going to divide your 14 (or so) golf clubs in your bag into four categories; driver, long irons, mid-irons, and short irons. These will correlate to four ball positions as well.
The driver category is the most self-explanatory of all, there are two clubs in it, your driver and 3-wood when hit off the tee box. The driver is fairly simple because it has the most obvious point of reference. The driver ought to be lined up off the inside of your front foot. This allows you more time to close the face and hit under the ball.
Your short irons category includes your 9 iron and all of your wedges swung full. The reason I've jumped from your longest club category above (driver) to your short irons is because these will be the two outside edges of ball positions. The short irons are hit with the ball in the middle of your stance. This can be easily found by starting your feet close together, ball positioned in the crease between your feet, and slowly widening your stance equally in both directions until you reach your desired feet width.
Your long iron category includes all of your fairway woods, hybrids, and longer irons (3, 4, 5). The long iron is placed slightly back from the driver position. Use the driver ball position as a reference point and move the golf ball back between 1-1/2 a ball width. This provides you the consistency on the longer clubs. Stick to this position even after a poor shot.
Finally, the mid-irons are your 6, 7, and 8-iron. Similar to the long irons and driver, the mid-iron ball position will use the middle of your stance as a reference point. Find the middle of your stance that would be used for short irons, and move the ball forward 1-1/2 a ball width. Again, perform this set-up the same every time for consistency and developing muscle memory.
In the end, your ball position isn't going to dramatically influence your shot, unless you do it different every time. If you're consistent in what you do, even if it's slightly off (1/2"), then you'll be able to hit better shots and have one less thing to worry about.