if you're not the online learner: some universities offer negotiation courses/programs which are sometimes even open to the public/alumni.
being able to understand and relate to people on an emotional level is a very important skill needed in negotiations, but a lot of it is also tactics and "playing the game".
I've read this book last year, and it offered me a lot of insight into the process of negotiations and also explained some pitfalls and offered valuable tools for running negotiations.
reading books and watching videos can teach you the theory behind it, but I think the dynamics behind it is best learned in real life scenarios eg a training program where you play through cases.
Third this. Available in digital, physical, and audiobook formats:
Title of this book is "Never Split the Difference" by Chris Voss. Very informative and the stories he uses to relate his points are captivating. One of the few books I'll read twice.
I recently read the book "Never Split the Difference" by Chris Voss, a book on negotiation by a former FBI hostage negotiator. It actually covered this, how the stereotypical sales tactics are actually pretty bad and he covers approaches that work much better. I highly recommend the book (or to watch some of his youtube videos).
 https://www.amazon.com/Never-Split-Difference-Negotiating-De... and his Youtube channel: https://www.youtube.com/user/NegotiationCEO