How do you know if a girl is ON to you?

Here are few guides you could follow,

1. She's trying to like the same thing you like: Example, if you're talking about certain types of music that you like, and she tries to give a positive opinion despite that she doesn't really listens to it, then you're scoring man!
2. Body language: E.g, does she crosses her arms? No is good. Does she brushes her hair round her ears? Yes, is good. Does she leans forward to the table when talking to you? Excellent!
3. She laughs at your stupid jokes: Clear sign of attraction
4. She tilts her head when talking/listening to you. You got it going man!
5. Touches you lightly when talking/kidding with you . What can i say more..!

Chris, is good at number 1, 2 and 5.