I guess I would consider myself great at "reading people" - their emotions and such. I do this by reading facial expressions, hand gestures, eye movements, even the way a person writes or types. I have become so adept, that I can tell when a person is lying by sensing a change in said person's heartbeat (by laying my hand on a person's chest). This is something about myself that I just sorta haphazardly discovered over the years. I gained such an ability due to my introversion and shyness. I've always been so quiet; I guess one could say, I've spent a lot less time speaking and a lot more time listening.
Quite frankly, I would not necessarily consider myself an expert per se, and admittedly my methods have some obvious flaws... :yes:
The term for this kind of thing evaded me at first, but I believe this is known as "profiling".