Do Conceal Your Emotions

Emotions - including body language - are like words: the more you express them, the more you give away. Try to keep a straight face that gives away nothing in particular. Avoid obvious expressions of relief or elation or panic! Anything you give away here will give clues to your counterpart.

You can of course try to use emotion or body language deliberately as a smokescreen. The problem here is that it is difficult to maintain the act, and sooner or later you are likely to be found out. The moment that happens, you will have generated some distrust. Your own standing and authority will be significantly weakened and your integrity questioned - rightly so.