Be aware and don't let your guard down. Even if you think the negotiations are going well, don't be lulled into complacency. Always be alert and vigilant and make sure you understand the ramifications of any agreement. It is like playing a game of poker. If you keep your poker face, it will be hard for the other side to interpret your moves. However, if you are tired or frustrated at the end of the day, you may sigh or let your face show how discouraged you really are.
Be careful what you say and how you say it. Everything you say should be planned and part of your overall strategy. Don't say anything off the cuff. It is important not to be too cocky or confident if the negotiations are going the way you want. Gloating or smirking can infuriate the other side. They will figure out that you got something you really wanted and they may suddenly get more aggressive so they can get something to gloat about. If you are asked why you are smirking, say you just heard a good joke and be prepared to tell one
On the other extreme, don't be too hesitant or informal. Don't be patronizing either. IF you give the impression that you are smarter that the other side, this can come back to haunt you. Usually it is best to have a neutral demeanor and occasionally have some emotion to show what is really important to you or to throw the other side off. It is all in the delivery. Let people know you are paying attention.
