You normally read that if you get a vibe from the girl that she enjoys talking to you (not even going as far as she finds you attractive) that you should push the interaction to a number or start flirting.

How do you do this when the girl is just acting polite and not really giving me anything to work with?

If this where happening with one girl, I'd move on. But this is a common problem. I can talk to them, but they never laugh, ask questions, or even smile necessarily. They just have a serious face even though I'm expressing myself in a genuine range of emotions.

Does this mean they find me physically unattractive?

Thanks