How to Read personalities by just looking at their face

I have been searching through Youtube and this one interests me. I can say that I am an introvert kind of person and I wanted that one to change, I want to gain more friends and I am not good at small talks, I just don't have that confidence, now something came out of my mind, It seems that I am a bit talkative when it comes to my classmates, maybe because I knew them already, I know how they reacts, I know their personalities.

Now, my question is; How can I get that same confidence when it comes to talking to a complete stranger. The answer might be simple, you just have to know their interest and from there you can get a topic to talk about and know their personalities.
BUT, there's a but right there, that will not always work.

Take a quick look at this video and learn how you can read someones life by just looking at their face and their body compositions.