Focus groups usually involve six to ten respondents in a group discussion lasting two to three hours, moderated by a skilled facilitator.
The facilitator will lead the group through a series of exercises designed to uncover their thoughts on the given topic. Good preparation of these exercises is vital, as is creating a democratic, supportive and informal atmosphere. The aim of focus groups is to get people talking freely and informally, so it's important that the people feel comfortable with the others in the room, otherwise they might go quiet.
The sample of people you choose to come to the session will usually represent part of your user group.
You could...
...ask someone to visualise responses to users' comments and bring them into the group for further discussion.
...use a video link or two-way mirror to allow the development team to observe. The session could also be videotaped for future reference.
Resources
Facilitator
Optional: Someone who can draw, if you are going to be using sketching
Video camera or room equipped with a two-way mirror