How do I ask for a girl's number on Facebook?

[Maxwell]

How to start a conversation on Facebook that will lead to getting a girl's number or even asking her out without being creepy or awkward? I have talk to this girl on Facebook before, and while talking to her I found out she had went to the same high school as I did, without knowing it. After her and I message each other, but it was quick, two weeks had pass and I messaged her again, we talk but again it was quick. But during those two weeks and even now she is on Facebook liking my statuses, so it's not she trying to avoid me.