Sometimes when I ask a girl for her #, she'll answer with a joke ("I don't know, you seem like the kind of guy who'd call, not speak, and just breathe on the other line), brush it off with a comment ("Nah, let's go do this instead), or flat out refuse.

How should you respond when a girl doesn't comply?

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D.G.A.F. isn't just a state. It's a lifestyle.

Make a joke then try again, when you get her laughing she is in an more emotional state rather than a logical one.

Her: you seem like a creepy stalker (or whatever it was)
You: Ehm..... that's pretty funny actually coming from you. Every one here can clearly see you are the most likely from the 2 of us to be a vicious serial killer. You probably do this all the time, talk to hot guys, letting them think they've met a nice girl at a party just to end up in 4 garbage bags in the bag of your car.

You get the idea, turn her reason around on her, exaggerate it a hundred times more to make her original comment seem so ridiculous, it's not even an excuse anymore :p

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You'll regret a 100% of the shots you don't take.

I'd make a total scene (no joke). I always make a scene if she doesn't complie. But that might not be the right tactic. Dunno, doesn't happen a lot actually and when it does happen why bother because it doesn't make sense to even try and recover.