Yeah, the few times I've cold approached in public and gotten a woman's attention, the conversation is in passing about whatever is going on around us but I always get caught up in not asking too soon on some "ha, yeah that's true so can I have your number now ?" shyt lol.I think if you are going to be the person initiating the convo you have to pay attention to the person's body language. If they are fidgeting or starting to look around, its time to close the deal. If a female stops what she is doing to talk to you (granted you didn't harrass her to), its a good sign. You don't have to trick her lol. Just do some small talk, wrap it up i.e. "well I gotta go or be somewhere blah blah" and ask for the number.