Summarize this article in one sentence.
Ideally, the topic of discussion should be important to enough people that you can involve people with significantly different interests or backgrounds. However, avoid the trap of making a topic so general or vague that the discussion becomes unfocused. If you are having difficulty balancing these goals, remember the topic does not need to be divisive. Some panels are created to offer advice or information, and these do not always have competing points of view on display. A panel of three to five people usually creates the most interesting discussion. Look for well-informed people from a variety of backgrounds. For instance, a member of the public involved in the issue, someone with experience working with the issue in a business or nonprofit, and an academic who has studied the issue. Create a panel with variation in age, gender, and ethnicity as well, as a person's personal background can have a significant effect on his perspective.  Inviting at least four people may be safest, in case someone cancels at the last minute. Invite these people several weeks in advance at a minimum, to allow them adequate time to prepare, and to give yourself time to find alternatives if one of them turns the offer down. Select an additional person not participating in the panel discussion, to serve as a moderator. Ideally, she should already have experience moderating panels. Select someone who understands the topic well enough to follow the discussion, and who is skilled in social situations. The moderator's main purpose is to keep the panelists focused on the audience, keep the discussion running smoothly, and help out the panelists when they stall. Individual chairs will make the participants appear closer to the audience than a solid table, encouraging audience participation. Arranging the seats in a slight circle, still mostly facing the audience, may help the panelists discuss the topic with each other. Include small tables or stands for holding notes, and provide a glass of water for each participant. Unless the room seats thirty people or fewer, provide at least one microphone for each two participants, and a personal microphone for the moderator. Consider seating the moderator in the middle of the panelists to help him address and guide each panelist efficiently. Keeping the moderator at a podium off to one side may make his job more difficult.

Summary:
Select a topic. Recruit varied participants. Invite a moderator. Plan the physical setup.