Criticism is futile because it puts a person on the defensive and usually makes them strive to justify themselves. Criticism is dangerous, because it wounds a person's precious pride, hurts their sense of importance, and arouses resentment.
Our trouble is not ignorance, but inaction.
Each party should gain from the negotiation.
People do things for "their" reasons, not ours. So find their reasons.
To be interesting, be interested.
Only the prepared speaker deserves to be confident.