I reckon most girls would pay alot of attention, get a convo going, acted interested in the convo etc. Maybe laugh at your non funny jokes. And smile. Oh, I almost forgot the classic. This is what my friends do. When a boy says something like a slightly jokey insult, they will lightly punch them or push them away, or say 'stop it' in a whiney voice. And then the boy will persist, leading them into a playful fight.
However I myself am the opposite, acting aloof and uninterested, looking away, staring at really boring things or at other people. I look completely miserable, make them think I have no interest whatsoever/they have no chance. Any little slightly jokey offensive comment which they make will result in me giving them the biggest evil and the silent treatment. A bit childish, I know.
So unless this girl is a weirdo like me, it should be quite obvious.