Understanding the signals that people send to each other by means of his body - a very useful skill. Some have them by nature, and some because of their negligence did not know how.
Author of the book "Body Language. Impressive, persuade and succeed with the help of body language, "Max Eggert made a list of 75 signs of body language, which, according to the writer, to help better understand the interlocutor. Website sure if the show a little diligence, you can easily learn to understand non-verbal signals.