This involves keeping a speaker's list and deciding how long each person will speak for:
Students also have time to negotiate individually and convince others of their propositions. This bit involves a free-for all of discussion and debate:
It's one of the most exciting parts of the year and students LOVE being given an adult way of discussing things. While some subjects might not find this exact format suitable I would encourage you to think about other settings you can simuate. Maths at a model stock exchange? Scientists at a science policy debate? Usually teachers are only limited by their imagination....