Agree. Just be confidence and funny like you did with the first girl (let's call her A). Also, I would add to ignore the new girl (B) a little bit for the firsts minuts. I mean, your attention must be focused on the person who earned it before (A) rather than B (she hasn't earned yet). Help B earning it. Get info by asking things to the both of them and use some negs (the neg's amount and intensity will depend on how hot and how confidence the girl is) A few weeks ago I met a girl in a house party. She was starting her carreer as a model. She was really pretty; taller than me... First thing she said to me: "Hey, that's the best shirt you had?". So I started to neg her and make funny of her in front of our friends. I knew I have to do it with intensity because she was sooo self esteemed.
Anyway; that was just an example. Chat with them for like 15 minutes top and then leave and hang around the club. Better if you go with some friends and between them you have a wing guy or wing girl. Do not ask for her number or show she likes you in front of people. NEVER. Once you and your friends have leaved the set (A & B), hang around the club and if you have the chance to isolate her later in that night, talk with her a little bit and do this: make her earn your respect and your attention; she has to know that she has proved si is good enough to talk with you; that she has something special or unique, worth enough to talk some more. Then use something to get her number. Maybe just open your phone and make her write her number (make a missed call so you make sure is not a fake number). That could work. But I am going to tell you a technique that has worked for me 6/6.
You: "Hey I need your help (maybe you can connect that to the conversation, f.ex. if she works with something related to technology)" or "Really? Then sure you you can help me.
Her: "Sure, what happens?"
You: "Something is wrong with my phone".
Her: "Really? What is wrong?".
You: "Your number is not in it..." (big smile)
I has worked for me everytime I tried it. Is just an example.
Well, I hope it is helpful. Tell us how it went!