One of the best ways I've found to deal with colleagues or students who talk too much during group discussions is to give them a task. I've found keeping a record of the conversation to be useful - not only for dealing with the problem of fair distribution of talk, but for tracking and assessing the quality of our conversations.

I have used different column prompts based on what I'm interested in with a particular group. For example, in the chart below, I wondered how often people were just "sharing" and how often people posed a question that generated a genuine discussion. I also wanted an overview of a typical comment made by each study group member -- over time, completed charts give me some material with which to do a discourse analysis. Once I begin to see patterns emerge in the conversation data collected, I might rearrange seating, put certain people together in talking pairs, play around with limiting conversational turns, etc.

Name	Check here if someone asked a question and got a response	Record the first words of a comment by this person
Grace
Anna
Nancy
Paul
Terry
Mike
Sarah
Tim
Josh

When a person is recording data, s/he is not talking (ostensibly) for that particular session. If the overtalker is my data-gatherer for a day, she has been given an opportunity to see what just listening feels like. We can talk as a group about the definition of "participation" in our classes. Sometimes engaged listening is just as productive and participatory as active dialogue.

I have also used charts like this a lot with my fifth grade students when we had literature circles and a few kids were dominating the discussion. Ironically, my big talkers loved being the data recorders -- go figure!
You can download a blank template of the "Conversation Turns" recording form by clicking on this link.