We all have greater or lesser non-verbal communication skills, just as we have verbal ones. They are just harder to get right!
My T and I discussed this issue once; she explained that she only works with verbal, what I tell her and what she can respond to. Yes, tone of voice, etc. get in there but if you start trying to find meaning in any particular crossing of the arms or legs (sometimes defensive) or jittery behavior (knee jiggling, toe tapping, finger twiddling, general restlessness) you come up against other possibilities that cannot be checked out very easily because most are unconscious. T's like to do a lot of reality checking, making sure they got what you said right and you can't do reality checking on an arm cross, the person might not even be aware they crossed their arms, much less know "why" and what they were thinking.
One thing I like to remember is that thinking, the head/mind, is all done in words and I am usually tangled up because of my words rather than my unconscious actions. Working with words; expanding my ability to put my feelings into words, express my thoughts to another (instead of having that stream of consciousness thing that goes on or knowing what you want to say but having it come out all jumbled :-)
My stepmother use to move her bottom jaw in front of her top jaw when she was angry. Her eyes would get "hard" and I, a kid shorter than she for quite awhile, would look up at this expression looking down at me and know I should not move a muscle or she might "snap" and hit me (or otherwise go into extreme, abrupt, scary motion). No words were spoken.
But think about the stuff one feels and then think about how helpful it can be to put it into words; my writing the paragraph above lets me literally "see" and capture what was going on. Feelings can be fleeting and, as they are about us and are our feelings, they aren't wrong, but what they might be telling us and what we decide they are telling us might be wrong. If you were doing face exercises and moved your lower jaw out in front of your upper one, I might be triggered, for example, think you were angry!
The feelings have to be put into words and the words said to check out what another is thinking, feeling, doing. Babies can get away with "different" cries to tell their mother they are wet, hungry, or need to be held but that's because they are only interacting with that one person and the person is an adult who wants to work with and understand that infants non-verbal communication. But out in the world, adult on adult, non verbal communication can be dangerous to try and read. Yes many can "generally" tell when someone's face registers anger, sadness, interest, boredom, fear, etc. but that is not very helpful in dealing with that person, other than to maybe give an opening conversational gambit ("You look like you are angry to me?").
Just reading faces "accurately" is a complicated science:
http://face-and-emotion.com/dataface...escription.jsp
For me, staying as close to "myself", working with my own thoughts, feelings, and actions as I can and not assuming I know anything about others helps keep me out of conflict and on good terms with myself and those I interact with.