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..