Is she smiling? Good. You're listening to her? Great. You're being honest with her? Perfect! Now... make her laugh. I know, easier than it sounds right? It may seem like a terrifying task but I assure you, it is completely worth the effort.
A girl's laugh (an honest one at least) is her best kept secret. She only offers it to those she truly likes when she feels comfortable and relaxed. And giggles don't count. You have to make her laugh, a real pee-her-pants kind of laugh. That is how you know you're on the right path; the one to her heart.
Just like a smile, this can be done in different ways. You can act silly, you can tell a joke, or you can share a story, whatever works for you, but know this; while there are no right or wrong ways to make a girl laugh, there are horrible ways to do it. Whatever you do, please (for the love of god), make sure she is not laughing at you but with you. It may seem trivial but it makes a world of a difference. It is the difference between love and friend-zone.
If you manage to play your cards right and laugh her laugh… this is where the magic happens, when her voice rings clear as a bell as she tilts her head back then leans forward to smack you on the arm and says "You're silly," that my friend, is when you know you’re in.