As a retail consultant, I'm called on to facilitate brainstorming, planning, team, culture, franchisee training, and the uncomfortable "things have to change" meetings.
No matter the audience or size of the group, people put up with a lot just because they don't set expectations at the outset.
Then they have to put up with someone droning on and on about "how we used to do it," or someone sharing their detailed explanation that tries to show how smart they are or someone stays silent because they are uncomfortable sharing their ideas.
That's why people hire me. I always draw this up on a board to focus everyone at the start, especially if it is an employee meeting over an extended timeframe.
My preacher dad once told me when people say, "Everyone feels this way," it usually means they feel that way. Encourage "I" statements throughout.
Time-suck and de-motivator to the group. If someone really feels that way, rephrase so it doesn't kill the spirit of brainstorming.
It is up to the moderator to make sure and call out participants who haven't raised their hands. Ask them if they agree with a certain point and why or why not so they can relax and share.
It is perfectly OK to lead or redirect an off-topic point with, "How does this relate to the point we are discussing?" If they can't answer, suggest they write it on a slip of paper and "park it" until you deal with everyone's parking lot issues at the end.
Need I say more?
Most meetings get stuck with individual concerns the rest of the group either wouldn't benefit from or do not share.
You might be challenged on a position or have to admit you don't know it all. That's perfectly OK, don't try. Read Avoid These 5 Common Presentation Errors
Brainstorming, in particular, is fragile. It's like the first draft of a story or song; you don't get a chance to return to that "What if?" moment. There will be plenty of time to look at logistics and "reality," but only one time to be inspired - keep it alive as long as possible.
A subject is being hotly contested but going too long to fit your agenda. Move on unless the majority votes to add five more minutes on the topic. Works every time. You'll be much more productive and have more to show for.
Bonus tips:
These are not all the ways to make an effective meeting, but the ones I've found as a facilitator could keep a group focused and deliver actionable ideas everyone could support.