First of all, I'm not smiling over all who are being judgmental at this post. The way to approach a woman is to make eye contact, so if she responds positively, then ask "Hey can we talk for a bit?" or, "We could like, talk while we're walking, I'm going to X place up here. If you're up for it." Then accept a yes or no. Do not try to persuade from here.

But the thing is hitting on her before she flirts back and confirms she's in it with you, isn't welcome. Just try to get to know her.