Do you remember that book published in 1981 called Getting to Yes by Roger Fisher, William Ury, Bruce Patton? It was and still is a very valuable and effective tool used in negotiating.
If you are interested at all in how that sort of thing works you might read the information
and even buy the book. I can tell you right now it really does work.
Wikipedia listed the four main components of the theory of negotiation:
1. “Separate the people from the problem2. “Focus on interests, not positions”3. “Invent options for mutual gain”4. “Insist on using objective criteria”
I just thought you might be interested.