Another way is from Kevin Hogan’ s Irresistible Attraction. This book is my Manhunter’s bible. Kevin says that you should maintain eye contact with your date (or potential date) about 80% of the time. That translates into a 7 second gaze and a 3 second look away, or a 14 second gaze and a 6 second look away. And this does NOT mean staring into the pupils until you are dizzy. You gaze into the eye nose triangle. One suggestion is to look from eye to eye then to nose repeated during a conversation.
Mr. Hogan also suggests that “flashing” your eyebrows ( a quick raise of the eyebrows,)is another way to signal someone you are interested. If someone “flashes “you, it is polite to “flash ” back. If someone doesn’t “flash “ you back they are either rude or not interested. “ Flashing” is fun, so just move on to the next “flashee.”
The next step is to after the “flash” or making eye contact for a few seconds, look down and the up again into his eyes. I taught this to my married daughter who did it to her husband. He immediately smiled and gave her a wonderful compliment. It WORKS! So practice, practice, practice.