While I have written eHow tutorials on mentalism aspects such as eye-accessing clues, this is actually a nose-accessing trick, so pay attention to the nose.
Hand your spectator a penny, or better yet, have him use his own if possible.
Begin by placing it in one of his hands and instructing him to place his hands behind his back.
Tell him to put the penny firmly in one of the hands while behind his back and close his fists.
Have him bring his fists from behind his back to the front, then tell him to concentrate on the hand it is in.
Instead of watching his eyes, watch his nose. If it moves to the right, it is in his left hand. Adversely, moving to the right identifies the left hand.
Repeat this for added effect, and even throw in the Divining a Memory trick (see Resources below) to utilize eye accessing in the same routine.