Studies have shown that most communication is actually nonverbal and that very little of the information that we derive from communication actually comes from verbal content.  In my years in various relationships and in carefully observing human behavior, I’ve come to associate certain behaviors, body positions and mannerisms with certainn underlying psychological states. Here is a very brief primer, including some of my (mostly) iron-clad 100% guaranteed observations over the years, broken down into two columns- the external observed action and the underlying psychological state responsible for that action:

External action……………… …………………….Underlying psychological state

Excessive unnecessary laughing or giggling- excessive nervous/anxiety; sexual frustration
Silence, especially after you give an opinion- disapproval or disagreement with the opinion
Looking up and to the left- person is recalling a memory
Looking up and to the right- person is visualizing a fantasy, such as a lie
Looking down- absorbed in emotions or feelings
Crossed arms- wanting to great distance
Smiling too much- social anxiety; wanting to be liked
Staring- passing judgment
Looking away when talking- either discomfort or deep disgust for the other person
Overly agreeing with everything- humoring the other person, condescension
Looking around quickly- wanting to get out of a situation, literally looking for an exit

Some of these are obvious, some are less so, and others are taken from practical aspects of NLP. Of course, most imporant is the context of the situation you are in. For example, if someone is not looking at you, they could be embarassed about something, but generally speaking if there is no apparent cause or reason, people tend to avoid looking at someone they have a negative opinon about. Look over this list and see how many times these situations pop up in your own personal relationships.