I've thought about this a bit further, and since you are trying to develop a sense for this sort of thing, maybe this might or might not help. Usually the easiest way to tell, for me anyways, is in talking to a person, doesn't matter what about, just small talk is sufficient and just see how that person interacts with you. Watch their body language, listen to the sound of their voice, where their eyes go, what sort of posture they have both before you approach and/or address them, and if it changes once you have... these are all things that factor into that sixth sense and if you train yourself to pay attention to them it may help you further it along in development and being able to recognize various "types" of people. Hope that helps some.

K