I think it helps a lot to pick up the non verbal cues a person is giving off and a lot of us do it naturally. However, I've always been put off by the "lying eyes" teaching. My eyes almost always naturally shift to the right when I am thinking because my left eyebrow typically also goes up. (I've done it for so long that eyebrow is actually slightly higher than the other). I just tried looking up and to the left with my left eyebrow arched and it feels weird. So weird. :-)
You are right...Body language isn't always right. Arms folded on the chest could indicate the person is cold for instance, rather than the person being closed off. It is situational. That's why I suggest some research on the topic and how body language can assist one to communicate more effectively.
I have found body language, and communications between humans, fascinating and so I'm passionate about the topic. I have much to report to my superiors when I return to my home planet. :)
Thanks for commenting.