Start with three balls place the first in the middle of your stance, then the second ball one ball over and the third one more ball over to the left. The rule of thumb is that the ball in the middle in your stance should be the proper position for your lower irons, say 7 thru the wedges, the second ball for your mid irons, the third position, just inside your left heal works great for the woods.   

 You want to catch the ball before the clubhead reaches it’s lowest point by setting the ball just before where the club makes contact with the ground. This will ensure solid contact and you’ll avoid hitting “fat” or thin shots.

Consciously trying to keep your head down does more damage than good, it can affect everything from posture in the set-up creating a too vertical swing-plane causing fat shots to creating so much body tension that the swing becomes stiff and unmanageable. Not only do you have the chance at hitting it fat you can miss the ball altogether by restricting your body motion and becoming inflexible and not letting the club swing.

So rather than keeping your head down, focus on how you stand at address. The proper posture will enable you to keep your head, neck and spine angle relatively still until after contact with the ball is made and the club naturally pulls the head up and around. This way you can admire your beautiful shot floating through the air. To attain the proper posture, follow these four rules:
1. Bend at the hips (stick your butt out!).
2. Flex your knees slightly.
3. Make your arms a relaxed extension of the club.
4. Keep your chin up.