Hear the "disruptive" contribution
A natural reflex: to ignore contributions that would carry us
away from our objectives. It is better however to hear them and signal
clearly: "yes, that's an interesting idea," or "that's a
point to keep in mind for later." But signal it briefly, without
elaborating further, since the very point is not to elaborate on the
topic that has been raised.
Review the meeting's plan
The organizer is the proper person to bring the meeting's order
back into view: its objective, its duration, its procedures or the rules
of participation in the group. We expect that he
assure it be followed, even if he must oppose certain wills to
do so.
Give each person the floor
It is essential in every meeting to aim at a fair distribution
of speaking time among the participants. This is even more true if some
of the participants seek to monopolize the floor. In
such a case you can ask the group their views, or even call on
each member, in order to equalize the speaking time and allow for the
exchange of ideas.