What?
Showcase or simulate situations, for instance a mediation situation or process in a particular case
How?
Try to involve all the relevant conflict parties; assign the particular roles (including the mediator) and clarify who is playing which role. Prepare statements and try to argue in the same manner the parties would do when at the negotiating table.
Remember the goal of the simulation is not to achieve “peace”. It can be even vital to show how hard mediation is.