NEVER GIVE A GIRL A COMPLIMENT ABOUT HER LOOKS - EVER.
Instead tell her she is smart and then follow up by asking her to teach you something.
She will be taken aback abit and she won't be able to answer right away - she will need time to think (20 seconds or so)
Then watch her eyes light up and she will start to open up and talk. You will need a few follow up questions to keep the dialogue going like "Oh thats cool, how did that happen or how does that work" etc.
She will leave this engagement and have you in her mind for hours.