Not the GP, but it's a book, 'Getting to Yes: Negotiating Agreement Without Giving In' by Roger Fisher , William L. Ury, et al. I read it ~30 years ago, the on

Not the GP, but it's a book, 'Getting to Yes: Negotiating Agreement Without Giving In' by Roger Fisher , William L. Ury, et al. I read it ~30 years ago, the only thing I remember is that you always want to understand your "Best Alternative to a Negotiated Agreement" (BATNA), e.g. knowing that you can walk away from a car dealer's deal, if you don't like the terms.