One of your roles as the meeting chair is to keep the discussion moving and on-task. Your role is not to offer opinion on every single issue or keep the discussion on an exact schedule. Have some flexibility. Let the other attendees talk freely and allow new topics of discussion to arise even if they're not on the agenda. You may find that you need to subtly end or change certain topics of conversation to keep the discussion on track, but you shouldn't feel as if you have to control every aspect of the meeting. After all, it's a collaborative process. As the meeting progresses, keep an eye on your agenda. If you're running behind, you may need to skip certain topics of discussion or table them for later in the interests of time. Don't be afraid to do this if the topics that are being discussed are very important ones. As the meeting chair, your job is to ensure an open, productive discussion. If you notice that certain attendees who may have knowledge relevant to the issues at hand aren't opening up to the group, encourage them to talk. You don't have to challenge or call them out directly — simply saying something along the lines of, "I think Mrs. Smith's expertise would be useful here" is a great way to get less-active members of the meeting engaged. It can be difficult to remember that not everyone attending the meeting has the same amount of experience or knowledge in the topics of discussion. To make sure everyone attending the meeting has spent their time wisely, you may want to take the opportunity to briefly simplify complex issues or topics when they come up. The less-knowledgeable attendees will undoubtedly appreciate this. If they're not kept under control by a competent chair, meetings can be remarkably unproductive. Try to make sure that every important issue you came to discuss gets addressed. Don't allow attendees to blame-shift or offer vague excuses for problems that haven't been addressed. Try to pin down and obtain answers for issues that no one wants to address. Though this isn't necessarily what every attendee will want, these sorts of awkward questions are precisely the ones that need to be answered the most for the meeting to be as effective as possible. Make sure important decisions are recorded (if you have official record-keepers or minute-takers, assign them this task). If you're going to go the trouble of asking the hard questions, you'll want to make sure that the answers you get are well-documented. There's a reason meetings have a bad reputation — for many, they're thought of as serious wastes of time. To prevent your meeting from running long, use your power as chair to keep the discussion moving. Don't be afraid to table certain unimportant issues or conversations until a later date if your meeting seems to be taking longer than you expected. Be ready and willing to adjust your schedule on the fly to make sure that none of your attendees' precious time is being wasted.

Summary:
Guide the discussion, but don’t dominate it. Encourage all attendees to participate. Make sure everyone understands what is being discussed. Don’t ignore difficult or awkward questions. Keep track of your time.