I want to see the person's face brighten when we are introduced. It can reflect friendliness, attraction on some level, an interest in me personally, or a general interest in making new acquaintances. If I don't see that small uptick in tension in the face, or a spark in the eyes, I know instantly that there are many other things more deserving of the next 2 minutes of my life than is this person, and my perfunctory hello is followed by a quick retreat. Life is too short, get out of my way!!!