Sometimes in club settings, when I'm sitting with a girl, I'll put the back of my hand on her leg when we're talking.

If she doesn't show a response positive or negative either way, should I take this as a sign to keep going? What's next? Should I put her legs over mine? Pull her legs a bit towards mine? Also would it be better if I used my palms instead of the back of hands (I've got sweaty hands)?