Observe the rhythm of topics and close old topics as they grow dormant. Consider time-delimited events or topics to foster activity. Don't pile too much into one post. Break it up into small paragraphs or multiple posts, especially if you are dealing with more than one point or topic. Don't obsess about typos.
Life is too short.
Facilitation is the combination of knowledge and practice. So practice, practice, practice. Read between the lines. Seek to be fair. Use common sense.