Browsing OkCupid, I just came across an HB8's answer to this question:

Q: Crowded bar, your eyes meet with someone you've already noticed as being attractive. You...

A: Leave it to chance- don't do anything.

Her explanation: depends what point in the night we are talking about. I'm shy, though and am likely to think he was looking past me or he saw something on my face....

Women want you to approach them. You make them insecure by not approaching, so approach already, dammit!

EDIT: Promoted her from HB7 to HB8 after seeing more pictures. One of those very rare instances of OkC pictures being less flattering than FB pictures.