Mediation is a good win-win method of the problem solving. In the books of mediation you can find some methods which can choose in the concrete case. In the study books find, how to use the mediation and caase studies as well.
If one considers mediation as an intervention strategy that aims at enabling people to sort out their differences themselves (instead of finding 'best solutions' for them), an appropriate model could be derived from Watzlawick's theory about more of the same-dynamics (that often operate in conflict) and their being driven by (nonverbal) relationship messages. Seen from that perspective, mediation effects should come forward as a decrease of antagonistic ('symmetric', fighting) relationship messages between parties, resulting in increased joint problem solving, negotiating (etc.) capabilities (Watzlawick, Beavin & Jackson, 1967, Pragmatics of Human Communication). See on the same subject: 'Less of the same' - an article in Dutch, with an English language summary - which I posted at Research Gate last week.