Focus on Interest not Positions
Negotiations start because both parties have an interest. They use their interests to develop a position. Conflict arises because each parties sees their position as the only way to succeed. And bot parties end up upset with each other or losing out on a lot of what they wanted.
That entire situation can be avoided. Don’t come up with your position before you talk to the other person. Don’t assume you know what they want out of the negotiation. Don’t dismiss their concerns.
Take the time to hear them out. Really listen and ask why. Explain the your issues while being supportive to the other side. Lay out all your interests.
Once all the information is on the table, you can work as a team.
Book: Getting to Yes