The time to develop such a relationship is before the negotiation begins. Get to know them and find out about their likes and dislikes. Find ways to meet them informally. Try arriving early to chat before the negotiation is scheduled to start, and linger after it ends. Benjamin Franklin’s favorite technique was to ask an adversary if he could borrow a certain book. This would flatter the person and give him the comfortable feeling of knowing that Franklin owed him a favor.
In consulting, I would ask to help out on releases with teams I had just met.
