How to run a brainstorming session
Last reviewed by The thinkdrop facilitation team
To run a brainstorming session, write the challenge as one specific question, invite 4 to 8 people with different perspectives, and set two ground rules: no criticism and quantity first. Give everyone five silent minutes to write ideas before anyone speaks, timebox generation to 20 minutes, then group the ideas into themes and leave with three owned next steps.
Key facts
- Group size
- 4–8 participants
- Total length
- 45–60 minutes
- Silent generation
- 5 minutes
- Idea generation
- 20 minutes, timeboxed
- Ideas to aim for
- 40+ before filtering
- Decisions to leave with
- 3 owned next steps
Step by step
- Frame one specific question — Replace a topic with a question. "Onboarding" produces nothing; "What makes a new user abandon setup in the first five minutes?" produces cards. Write it where everyone can see it for the whole session and refuse to widen it mid-session.
- Invite 4 to 8 people, deliberately mixed — Below four you get one person's opinion with witnesses; above eight the quiet half stops contributing. Include at least one person who is close to the problem day-to-day and one who is not — the outsider asks the question everyone else stopped asking.
- Set two ground rules out loud — No criticism during generation, and quantity before quality. Say them at the start rather than assuming them. The first evaluative comment in a session sets the tone for everything after it, so name the rule once and enforce it once.
- Generate in silence first — Give everyone five minutes to write ideas independently before anyone speaks. The first opinion said aloud anchors the room, and research on brainstorming consistently finds that individuals writing separately produce more distinct ideas than the same people talking. Collect the silent cards before opening discussion.
- Open the floor and build, timeboxed — Run 20 visible minutes where people read each other's cards and add to them. Use "yes, and" rather than "no, but". Keep every idea on the board, including the impractical ones — they are the raw material for the ones that work.
- Group into themes — Cluster the cards into five to eight themes and name each cluster in the group's own words. Naming the theme is the moment the session turns from a pile of ideas into an argument you can act on.
- Choose and assign three next steps — Let everyone react to the cards, take the top three, and give each one a named owner and a date. A brainstorm without owners is a meeting people stop attending.
Why most brainstorms fail
Sessions rarely fail because the team lacks ideas. They fail in three predictable places, and each has a mechanical fix.
- The question is too broad, so every answer is also too broad. Fix: one specific question, written down.
- The loudest person speaks first, so everyone else converges on their framing. Fix: silent generation before discussion.
- No one owns the output, so the ideas expire in the notes. Fix: three named owners before anyone leaves.
Facilitator behaviours that change the outcome
The facilitator's job during generation is not to contribute — it is to protect the rules. Restate the question when the group drifts, write down ideas people say out loud so they are not lost, and interrupt evaluation with "park it, we'll judge after the timer". During grouping, the job flips: push the group to name themes precisely rather than accepting vague labels like "communication".
Running it asynchronously
For distributed teams, open the board 24 hours before the call and let people add cards on their own time. You arrive at the live session with 40 cards already on the board and spend the meeting on grouping and deciding, which is the part that genuinely needs everyone present.
A 60-minute agenda that works
| Time | Phase | What happens |
|---|---|---|
| 0–5 min | Frame | Read the question aloud, state the two ground rules |
| 5–10 min | Silent generation | Everyone writes cards independently, no talking |
| 10–30 min | Build | Read each other's cards, add and extend |
| 30–45 min | Group | Cluster into 5–8 named themes |
| 45–55 min | Prioritise | React and vote, pick the top three |
| 55–60 min | Assign | Owner and date for each of the three |
Frequently asked questions
How many people should be in a brainstorming session?
Four to eight — fewer produces one viewpoint, more silences the quieter half of the room.
How long should a brainstorming session last?
About 60 minutes, with idea generation timeboxed to roughly 20 of them.
Should brainstorming be silent or spoken?
Both: five silent minutes first, then spoken building on what everyone wrote.
What is the most common brainstorming mistake?
Evaluating ideas while they are still being generated, which stops people offering anything unfinished.
How do you end a brainstorming session?
With three chosen ideas, each having a named owner and a date, not with a list to review later.