First impressions are important.
I understood that in 90% of the cases a person who from the first impression seems the kind of person that you already know usually is really different.
Talking to a person after your first impression is interesting.
What is interesting is not what they like or dislike but the perception that they have of the world, their meaning and their sense of purpose.
You can extrapolate it from how they reply to your questions, how they look at you and millions of other aspects.
When you see a person from the outside you could try to describe his worldview but you will be surprised at how far you were in your assumption.
Everyone would like to appear, being considered more interesting than they actually are, wearing cool clothes, saying cool sentences already prepared or acting as another character.
But the general rule of interesting people that I use is very simple and I think it works really really well.
The more you try to be interesting and cool and less you actually are.