Technically, yes - they should be right under the ball of your foot. Unless you like the feeling better with them forward or back. But you've got it right - start with them under the ball and only adjust them if you feel they are wrong/could-be-better. It's also necessary to dial in the "twist" of the cleat. You want them set so that when your foot is in its natural, neutral position on the pedal cleat is clipped in right in the middle of its lateral float.
C