Negotiating a deal is tough if you don't have a lot of experience with it. Forbes points out that one simple thing everyone can do to negotiate better is let the other person talk first so you're given the opportunity to strengthen your hand.
Photo by Zach Taylor.
The idea here is that you want to get the other person to show their cards so you can come up with a better reply. So, let them talk first and get their ideas out there. Then, Forbes suggests you walk away from the discussion:
Once you've heard the other side's arguments, set a date for another meeting. Then leave the bargaining table. By letting them go first, you've allowed them to vent, and potentially gained some valuable information. That helps you come back in a slightly better position.
From there, things ought to basically follow this formula: figure out where both sides have any areas of agreement; then continue exploring until you have found a mutually agreeable objective.
You certainly can't always walk away to think about every single thing you negotiate, but a little distance from the situation when possible gives you a chance to come up with a strong position for your argument.