Make sure that your participants know that you respect their time. Do a round of introductions, even if you think most people know each other. Review the agenda and, if appropriate, minutes from your last meeting. Create group rules or ground rules. Creating ground rules can be as simple as getting an agreement from everyone that you will stick to the agenda, or that they will respect those who disagree with them.
Ground rules can help create community and guide the discussion if things get out of hand.
Help move others to action. After an appropriate amount of discussion, call for someone to make a motion or get a commitment to a decision. Seek concrete commitments from people. If your group makes a decision to hold a press conference next Friday at 10 a.m., make sure that people leave knowing who is going to do what. Create a signup sheet on butcher paper and write people's names on it under different tasks in big letters.