If you had to tell someone's future, how would you go about it?

I just asked someone, kind of as a joke, to tell me my future. Then I started thinking about how I would do it. I often get feelings about people—maybe not their future, more about their past or who they are. But I think that leads to the future. I’ll talk more about it later.

How would you do it? Would you use voodoo? Cards? Tea leaves? How about data? How about interviews? What would you do?