you're thinking too hard and trying too hard to entertain her. she eventually looks down on you cause you're trying so hard to make her laugh or feel good. a lot of women want something to pursue a little as well. you have to find that balance.
don't try to be Mr. funny so much but don't try to be mr. too cool either. when you approach her, chances are she knows what it is. you do a little small talk, check her vibe, if she's warming up to you, say "I like this conversation, we should hang out sometime (smile genuinely) what's your number? (while pulling out your cell). Or something like that. no need for something very elaborate or special. no need to impress her. you just need her to find you decent and respectable enough. i think too many dudes need chicks to find them amazing, funny, witty, smart for their own ego. fukk your ego. be the almost boring guy who is trying to get at her but doesn't depend on her for an ego boost or validation. all that extra shyt is for street entertainers. dudes are doing so much they might as well ask for donations in their hat.
some extra advice, when you get the number, tell her exactly when you will call her (and call at that time). this is good for the both of you because it eliminates a lot of the phone games. either she will answer or she won't. it will feel different to her because she knows she has something to anticipate. you're also teaching her to follow your lead and your pace and that you know what you're doing. when you eventually set up the meet and get more intimate with her, going along will seem more natural than not cooperating because then it would put her in a position where she has to lead the pace.
EDIT: and also, this is why it's better to approach girls that are already feeling you. the girl that gave you the greenlight to approach her. that way you're not even thinking about impressing her. she already has a little bit of attraction to you.
and you're asking me?
