Im having difficulty going from mindless chit chat to actually getting a number from a girl. I can happily give them mine. Everyone says to say you gotta be somewhere and ask if you can continue the conversation later but some times this doesnt quite work out. I can talk all day to anyone, I need to learn to shorten my openers right down to getting a number within a few minutes. Say if I'm in a mall, I see my target, chat some bollocks about what to buy my sister for her nonexistent birthday, its gonna sound a bit shit if I say "give me your number and we can continue this conversation later"... as in we're going to continue the conversation about my sisters present later?!... That'll just sound lame in my eyes. How can I be talking to a girl and turn that into extracting a number?

Mindless chit chat is cool...but make sure it includes something entertaining, a random story that conveys energy and humor, this allows you to build both comfort and attraction...
Then when you can tell your target is really engaged tell them that you have to be leaving..this usually results in the target looking sorta bummed that the plesant interaction has ended, from here you can continue with cocky/funny and say: hey don't look sad, tell ya what, you give me your number and I'll call you sometime... (then throw in a softner when you get the number so you don't look needy...and say thanks maybe I'll call you when Im drunk and lonely *hahha* credit to T) but remember to hang around a little while longer after you get the number another wise you'll look like a sleeze that's just after the number..

Perfect!
Muchos Gracios Amigo