Once you have welcomed everyone and quickly laid out the ground rules, it is important to introduce the topic for the dialogue as clearly and as briefly as possible. Try to provide a context for the issue you will be discussing and to suggest at least two different sides of the story. Remind participants that the purpose of this session is to explore many different points of view and to seek common ground or at least a better understanding of other peoples point of view.
If you are hosting a more goal-oriented dialogue, tell participants what you hope will emerge from the discussion.
Be as clear as you can on your objective while making it clear that the most critical issue is that participants feel free to speak openly about their points of view on the topic/issue.