Meetings without a clear purpose or end goal. I think that these are "feel good" meetings that sometimes have a place, but should not be 100% of all meetings. These are the meetings that stray off the path of being productive into venting about the current state of something or exploring "it would be great if..." scenarios that are unreasonable to do. Everyone feels good because they get to talk about these things, then nothing happens from that discussion. If the topic is too broad, that is all that really can be done.
I think the way to avoid it is:
Meeting agenda ftw.
And someone with the power/authority/cohones to enforce it. Whether it's a "producer"-type or tech lead that plays the "bad cop" here, once the agenda is finalized at least one person in the room needs to be able to keep it. Follow up meetings are a sane way to truncate tangents, convoluted discussion, etc.
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