Eyes are like doors to the soul. They will show the attraction about someone.
The first signal that he wants you is eye contacting. Especially he will look at you many times. When you trying to look him he will catch your eyes into his eyes.
Secondly you can count his eye blinking. They are quick. The count also will increase.
Thirdly, the pupil size will change. When you respond to the light the pupil size will change. Physical and psychological attraction will change your pupil size.