You should know / have decided
You should have the first version of the system specification (overview, customers, goals, system functions, system attributes).
You should have high level use cases for all of your functions, and you should have ranked them.
You should have expanded use case for at least the primary use cases. (This is a task that can easily be split between team members.)
One or more of the teams will be asked to put up one of their expanded use cases for discussion. The other members of the tutorial will give feedback primarily on the content, but also on the presentation if appropriate. It is best to ask questions such as "What about ?" or "Why did you do ?" rather than criticise "You are wrong!". This is primarily an exercise in learning from each other.
If there is any time left after this exercise, teams can work on their conceptual models.
One or more teams will be asked to put up their conceptual model and / or a sequence diagram. The sequence diagram will be tied to a use case. Come prepared.