For a bit of perspective, early teachings on negotiation focused on hard bargaining. Under this approach, negotiators would fight to control cursory aspects of the negotiation (such as where the discussion would be held) and employ take-it-or-leave-it tactics. Though successful from a position of unquestioned strength, this approach made agreement less likely and was detrimental to relationships.
In reaction, members of Harvard's program on negotiation proposed "principled negotiation" strategies that involved focusing on interests, exploring options for mutual gain, and leveraging BATNAs (best alternative to negotiated agreement) when seeking concessions. However, these strategies are directed at one side of the negotiation and struggle with questions about how to deal with a deceptive or overly competitive opposing negotiator. Co-resolution skirts these problems by aligning the strategies of both negotiation coaches. Therefore, the following approach can be used by both co-resolvers in coaching the disputants to negotiate under their highest values and aspirations.
Preparation:
Starting at the upper left corner of this flowchart, the coach listens to the perspective of their own disputant, breaks down this input into underlying interests and the component parts of the issues in dispute, and ranks these elements from most important to least important to the disputant. The co-resolver then observes the values motivating the disputant and asks the disputant how they ideally see themselves negotiating with the other side. The same analysis is then applied to the other side, and these inquests can occur during both joint sessions and caucus.
Dividing up the perspectives into smaller elements and underlying motivation is vastly important. A negotiation will be more flexible and more likely to reach resolution when as many possible aspects of the disagreement are on the table. Also, breaking perspectives down into smaller pieces guides the co-resolvers and disputants into better understanding the dispute. Finally, because people tend to see themselves as reasonable, identifying and anchoring the disputants into their self-perceived values will motivate them to act as their best selves at the negotiation table.
It is also important to analyze the BATNAs of each side and the zone of possible agreement between them, because this defines the leverage and power differential between the disputants. However, the BATNAs are at the bottom of the chart because the co-resolvers should coach the parties to negotiate with their higher interests and values before resorting to power struggles. Also, aside from the goal of conducting the negotiation using values instead of power, BATNAs can be unreliable or dangerous as the basis of bargaining. Especially in negotiating disputes (as compared to business deals), disputants have different and inflated senses of their alternatives to a negotiated agreement--if both sides believe they will win in a court battle (you don't have to be an attorney to tell them this is not possible), then neither side has incentive to reach a negotiated agreement.
Negotiation:
Before beginning the negotiation, the co-resolvers need to prep the disputants into the negotiation mindset. In joint session or initial caucus, each co-resolver should explain to their disputant that, because the only possible outcome of the process is through agreement, that they need to identify what they want and persuade the other side to want the same things. The co-resolvers should also convince the disputants that they need to get inside the other side's head and, to do this, they must attempt to understand their desires and motivations.
Once the disputants are in a healthy frame of mind, the negotiation should begin with a conversation before offers and requests are exchanged. Here, the disputants should be encouraged to discuss their differing perspectives and attempt to understand the other side. This storytelling phase should be conducted in a relaxed, informal manner. Co-resolvers should remind their disputants to provide reasons for their actions and expectations.
After this exploratory phase, each side can begin to structure and exchange offers and counteroffers. Every offer is both influence (affecting the other side's perspective and expectations) and information (revealing your sides expectations and abilities). The choice of whether or not to make the first offer is a balance between anchoring and uncertainty--the first offer tends to affect the other side's expectations ("anchoring") but can also give away too much. Therefore, the first offer can be beneficial but should be reserved if your side is informationally disadvantaged. Each side should be encouraged to open with an offer that they can justify as acceptable to the other side. Counteroffers are then exchanged as alternative perspectives on what is reasonable. Concessions between counteroffers motivate movement through reciprocity and leave both disputants satisfied that, even though they gave up some demands, the other side gave up demand as well.
Through these steps, the disputants work towards building a mutually-acceptable agreement. The first step towards this goal is to define the disagreement, bringing the disputants to explain the parameters and reasons for each element of the disagreement. The co-resolvers should then expand the scope of the negotiation, explore trades between these smaller components, and encourage their respective disputants to benefit the other side in exchange for concessions. Using the above chart, the co-resolvers can direct the disputants to apply the other side's values to their own interest in making requests and apply their values to the other side's interests when making concessions.
I like this last idea, so I will repeat it. When making requests from the other side, take their values and frame these values in terms of meeting your side's interests. Then, when convincing your disputant to make impactful concessions, use your disputant's values in coming up with ways to meet the other side's interests.
The above ideas are only suggestions, and each team of co-resolvers should build their own methodology that they find comfortable and natural.