I've noticed when I've talked to a woman and the conversation is going well, something in their eyes change, not sure if it's dilation or what, but it's some little subtle thing that I notice when I feel they're attracted to me. Like a little twinkle or something or like they're smiling with their eyes while they're talking to me. The eyes are the key. As they say, the eyes don't lie. That's why a lot of poker players wear sunglasses. I've always been a sucker for blue or green eyes on women. Nothing beats staring into a gorgeous pair of eyes haha!