“Spend at least twice as much time preparing… as you expect to spend at the table.”
The #1 emotional sign that a negotiation has gotten the best of you isn’t anger or disappointment — it’s surprise. Most people don’t behave erratically or without reason. They make the most rational decisions they can with the information available to them, and sometimes even signal their intentions beforehand.
If the success or failure of a negotiation is going to impact you for years to come (even if the deal is as small as choosing one used car over another), why wouldn’t you invest at least two hours of your time researching and preparing for the negotiation?
With thanks to: The Harvard Program on Negotiation