If either party to a disagreement is too emotional to be logical, the conversation should be deferred. Pausing a few hours or even a few days in cases where decisions do not have to be made immediately is sometimes the best approach.

Making suggestions and questioning are not the same as criticizing, so don’t treat them as if they are. A person making suggestions may not have concluded that a mistake will be made—they could just be making doubly sure that the person they’re talking to has taken all the risks into consideration. Asking questions to make sure that someone hasn’t overlooked something isn’t the same thing as saying that he or she has overlooked it (“watch out for the ice” vs. “you’re being careless and not looking out for the ice”). Yet I often see people react to constructive questions as if they were accusations. That is a mistake.

If it is your meeting to run, manage the conversation.

There are many reasons why meetings go poorly, but frequently it is because of a lack of clarity about the topic or the level at which things are being discussed (e.g., the principle/machine level, the case-at-hand level, or the specific-fact level).

Make it clear who is directing the meeting and whom it is meant to serve. Every meeting should be aimed at achieving someone’s goals; that person is the one responsible for the meeting and decides what they want to get out of it and how they will do so. Meetings without someone clearly responsible run a high risk of being directionless and unproductive.

Be precise in what you’re talking about to avoid confusion. It is often best to repeat a specific question to be sure both questioner and responder are crystal clear on what is being asked and answered. In an email, this is often as simple as cutting and pasting the questions into the body of the text.
