Speak your mind. In full, passionately and with energy and enthusiasm.
You know, if you're saying something you don't
really mean, it stands out a mile off. How often do you speak to someone, and you wind up with just this instinctive feeling that they're not quite being straight with you? (Watch Nick Clegg speak, you'll probably have that same feeling
)
I think as humans we're programmed to detect when someone is being less than authentic with us. We're programmed to scan someone's demeanour and match it with what they're saying. If the two don't tally, then you're left feeling uncomfortable. Alarm bells start ringing. The person is being inauthentic with you.
The easiest way to get around this is simple: Just say whatever the hell you want to say. Whatever's in your head. Get it out there. Express yourself using your voice, and then prompt her to express herself using her voice. This exchange of expression, when done sincerely, is what builds rapport.
You don't have to have a girl wetting herself with laughter to attract her. Just be yourself, show her who you are. If she feels you're being authentic and sincere with her, then she knows its safe to open herself up to you and return the compliment. That's when you connect with someone.
Speak your undiluted mind with vigour and purpose, and let go of the notion that you need to impress her.