This may seem obvious, but it is often forgotten as organizations experiment with the Internet. Different purposes dictate different designs and technologies. Signal clearly, and regularly, the objective and tone of your discussion. Because people tend to migrate in and out of Internet discussions just as they come in and out of working sessions in physical conferences, it is important to assure that people know the purpose of the list, as well as the ground rules and the general ethos and tone of the discussion. Moderation, as Aristotle reminds us, is key.
Tools are just tools.
Avoid the temptation to use the most sophisticated on-line tools available, unless they are specifically suited to your purpose and your audience. Capture the learning, and make it easy for others to access. The best discussions don't necessarily go on forever. Lists that go on for too long can lose focus, particularly if they are not tied to specific actions or decisions. If the objectives of the list are clear, the discussion well-moderated, and the participants committed, a list can continue indefinitely.