Reddit mentions of Neuro-linguistic Programming For Dummies (For Dummies (Psychology & Self Help))

If you wanted to know whether you're missing out on cues, this should not be that difficult to test. Baron-Cohen has put some tests online that measure empathy; a similar but interactive test could be administered by a trained psychologist within the space of a single 1h session.

There is a subset(?) of nonverbal comms that you can train consciously, just as you would consciously train elocution. Have a look at neuro-linguistic programming (NLP). There are unfortunately many people who purport to teach NLP without knowing the first thing about it, so if when you read or experiment with something you feel it is hogwash, chances are it is.

Perhaps the easiest techniques/cues are the following two:

proxemics (distance management)

You can tell how much confidence, trust, and intimacy there is between two people by how close they stand or sit next to each other. This is quite easy to experiment with and get a grasp on, as you can read the other people's reaction even without being good at social cues: if you are too close, they will move away, block (see below), or become uncomfortable. You can observe how people behave when they are comfortable/uncomfortable and develope your understanding further from there.

blocking

http://www.study-body-language.com/Defensive-body-language.html — be aware that sometimes folded arms or legs just mean that the person is feeling cold / has a short skirt and wants to be decent. The 80/20 rule applies: most of the time things are what they seem to be, but often they're not. Often the easier way to eliminate false positives is to ask: "Are you cold?" — "Yes, I'm a little bit cold."; I have learnt to verbalise and comment on cues as I go, and people do find my accurate observations amusing, as I often know what they're feeling before they do :-)