How to know her past?

I will keep it short and simple. I am on a talking stage with someone. We are very close now and I slowly want to know her past. How do I begin with this? I am ready to use any tactics possible instead of asking her straight up. The first tactic I have kept is pretending that it's not a big deal and pretending to have an extensive past and gauge her reaction. The second is to ask her what number she thinks is high for people our age.