Private Investigator Tricks

I really love old detective movies, and lately I have been doing some detective work myself. I wanted to track down a girl who used to be in the same classes as me, and I figured there must be some kind of detective techniques I could use to find her.
I was actually quite successful - I found her. Using the skip tracing techniques on this private investigator website I managed to track down several leads, one of which revealed her phone number. I sent her a text message, and we are meeting up next week!