Start with one question.
Decide which relationship or decision the group needs to test: shared communications, who can order an evacuation, hospital surge, trusted public information, or support for people with access needs. Invite the people who own those decisions. A smaller group with real responsibilities is more useful than a crowded room of observers.
Give participants only what they would know then.
Describe a plausible emergency and release a few short updates as the discussion progresses. Ask each participant what they would decide, whom they would tell, and what information they need. Keep attention on life safety, command, coordination, continuity, and recovery. Avoid rehearsing attacker methods.
Record the gap and return to it.
End with three things: what worked, what was unclear, and who will fix each gap by a specific date. Review the corrective actions with the same partners. A tabletop is valuable when the next response is better.
More: FEMA HSEEP resources