Perhaps this has been raised elsewhere and I'm stating the obvious, but it has occurred to me that for direct openers, there needs to be enough time in the opener for the girl to:

A) understand the person is not a threat/salesman/charity worker etc. B) assess body language, eye contact and attraction. C) decide on response.

In my experience, there is a risk or startling someone with a snappy: "hey, you look cute and I had to say hello".

Whereas a relaxed, smooth: "Hey [momentary pause/good EC], I saw you from across the road there [momentary pause/smile/good EC], I just though, I had to come an say hello", will get a stronger and more comfortable response.

Thoughts and clarification appreciated!