Treat everything with skepticism. Not necessarily to see everything as a blatant lie, but a necessary share of skepticism in the analysis of incoming information and cross-checking on important occasions.
Try to be as clear as possible the psychological portraits of his companions. Study the literature on behavioral psychology and manipulating people in order to know, when you apply a particular technique.
Every word that man says, there is a motive – it must be clearly traceable. In most cases, humans pursue the same motives, and if you see that the one motive that is clear, distracting from the overall list, be on the lookout. The option in which the motive can not be traced clearly deserves twice the attention.
Ask people directly what they need, what they want to achieve. Generally if the thoughts of man are pure, it will not be long to think and expressly stated its purpose and your role in achieving it, if you see that the person picks up words and doubts – don't take on faith what he says, analyze his sentence based on his needs in the here and now.
More practice in dealing with people. The more you talk, the easier it is for you to distinguish between manifestations of human lies and the easier it is for you to reveal the hidden thoughts.