Typically the product group would organize the session with the internal team, One of the tester (also sort of semi owner of the feature) would give a brief about the feature, a small discussion would then take place of how, where and who and that's when the shit hits the fan; questions start pouring in one after the other, all of these questions are really different scenarios and typically when no questions are left the brainstorming is concluded.
Anchoring is what causes this damage and kills the objective behind the brainstorming itself. It always is a challenge in brainstorming sessions, something like the 1st idea that gets discussed is the one that kills the creative originality of any potential idea(s) that could turn in later. Once the first idea hits the floor, everything you discuss is around that idea.
A brainstorming can be made effective by:
1. Right People
Involve the right people, one that are spectators would not be of help and may just divert the focus of the group by asking questions just to prove that they are a part of the group discussion. People with appropriate knowledge in given area are needed to be given preference over those in the org charts. Senior Managers should be given a attendee hat in the first part of the session, to avoid the low hanging fruits getting picked first and diverting the focus.
2. Divide in groups
Brainstorming sessions are effective only if the group is divided and has different ideas on the table to discuss. Brainstorming can be more effective in a group divided with different base ideas, allegiances.
3. Cap the time
A time cap should be levied on the participants, so the brainstorming isn't hijacked. Ofcourse the moderator can allow participants on a case by case, but then the vocal participants can end up taking over the session and at times without having fruitful discussions.
4. No repeat, No Blocker
A lot of brainstorming sessions end up repeating the same ideas, topics, points by different attendees. This is a NO GO. Just moderate when that happens. Ideally a whiteboard can be handy so everyone can see what is covered and what is not. I attended a brainstorming on City Civic issues and the group actually put up a list of items they wanted to cover, allocating time to each point. Everyone was free to add to that list but the moderator was deciding the time. This gave a good start as several ideas started turning up when some items were discussed and by the end of first 3 ideas almost 20% of items made new to the list and some got dropped.
Never forget to conclude the brainstorming. If no actions, no tasks , no objectives or goals are defined within the brainstorming session, likelihood is you have just wasted that time with no yield. List the actions and dont forget to follow up.
A few dedicated effort in preparations, organizing the topics, execution can help the brainstorming be fruitful. The goal needs to be concluding post all ideas are discussed. I have also liked Candour a tool to collect and collate ideas. Next time you are brainstorming, turn the Q&A to a real discussion. Share your ideas, just not be interested in questioning or challenging others.