Act Dumb

To skilled negotiators, acting smart is dumb. Actually acting dumb is brilliant. When you are negotiating, you’re better off pretending as if you know less that everybody else does, not more that they do. The dumber you act, the better off you are. Unless the other party is fully aware of all your credentials.
There is a good reason to act dumb in front of the other party. With a few exceptions, human beings tend to help people that they see as less intelligent or informed, rather than take advantage of them. Of course there are few people might take advantage of weak people. Generally people become competitive when among a smart group, or become helpful when dealing with people who they think are inferior to them. So, the main reason for acting dumb is to diffuse the competitive spirit of the other side.