Interesting subreddit. I'm no PUA by any means (beginner)--apparently I have AA most of the time.

However, I've always used this line with girls that are alone (mainly), not smiling, or texting too much. What can be even better, is you have to use it quickly--hot girls don't stay alone for very long. It generally elicits a smile and an explanation, and can be used at bars or during the day. Anytime you see a girl doing something she probably doesn't want to be doing...it can work.