What interviewers want from a brainstorm
A brainstorming question, like 'what are some ways this company could grow revenue' or 'what factors might explain this decline', is testing your ability to generate ideas broadly while still organizing them logically. A candidate who rattles off ten ideas with no structure looks less impressive than one who offers six ideas grouped into two or three clear categories, even though the raw idea count is lower. Structure signals that your creativity is disciplined, not scattered.
Structuring ideas into buckets instead of a list
Before listing individual ideas, state the categories you'll brainstorm within. For 'ways to grow revenue', a reasonable structure might be: growing the existing customer base, increasing spend per existing customer, and entering new markets or segments. Then generate two or three specific ideas within each bucket.
This turns a scattered list into something that reads as deliberate thinking, and it also makes it easier for you to check you haven't missed an obvious category, since you're scanning bucket by bucket rather than free-associating without any anchor.
Go for breadth first, then depth on the best ideas
Generate a reasonably wide set of ideas across your buckets first, without evaluating them yet, then come back and identify which two or three are the strongest or most worth exploring further. Interviewers often follow a brainstorm with 'which of these would you prioritize and why', so having already thought about relative strength puts you ahead of that follow-up rather than being caught flat-footed by it.
Avoiding the laundry list trap
A common mistake is trying to maximize the sheer number of ideas mentioned, which tends to produce a laundry list of shallow, sometimes redundant points. Quality and organization beat quantity here. Five well-explained ideas grouped into clear categories, each with a sentence of reasoning for why it would work, is a stronger answer than fifteen bullet points fired off rapidly with no explanation behind any of them.
A brief example
Question: how could an airline increase ancillary revenue? A structured answer might group ideas into pre-flight (seat selection fees, baggage fees, priority boarding), in-flight (food and beverage sales, wifi access, entertainment packages), and post-flight or loyalty-based (co-branded credit card partnerships, points redemption fees). Presenting it this way, categories first, then examples within each, shows organized thinking rather than a random brain dump, and it also makes it easy for the interviewer to ask a targeted follow-up about any one bucket.
How to prioritize when asked which idea is strongest
When asked to pick the strongest idea from your brainstorm, use a simple, explicit lens rather than an unexplained gut pick: which idea would have the biggest financial impact, which is fastest and cheapest to implement, and which carries the least risk or dependency on factors outside the company's control. Naming the lens you're using to prioritize, even briefly, shows the same structured thinking that made your initial brainstorm strong in the first place, rather than switching to unstructured intuition at the finish line.
Staying structured when the clock is running
Brainstorming questions often come with an explicit or implicit time limit, and the pressure to fill the silence can tempt candidates to abandon structure halfway through and just start listing whatever comes to mind. Resist that. It's better to present three well-organized ideas within your allotted time than seven scattered ones, even if it means consciously cutting yourself off before you've said everything you thought of. A calm, organized answer that ends a little early reads better than a rushed one that keeps going past the point of usefulness.
Grounding your ideas in the specific client's situation
Generic brainstorms that would apply equally to almost any company in that industry tend to feel weaker than ones that clearly connect back to details already established earlier in the case. If the case mentioned the client has strong brand recognition but weak distribution, an idea list that leans on that brand strength while addressing the distribution gap directly shows you're synthesizing across the whole case rather than producing a stock answer you could have given without any of the earlier context.
What to do if asked to brainstorm again later in the case
Some cases include more than one brainstorming moment, often once early to explore the problem broadly and once later to generate solutions after a root cause has been identified. Treat these as distinct exercises with different goals, the first is about exploring possible explanations, the second is about generating possible actions given what you now know. Conflating the two, for example still listing possible causes when asked for solutions, signals that you're not tracking how the case has evolved, which undercuts an otherwise strong performance.
Treating the brainstorm as a bit of a dialogue
Even though a brainstorm question is largely you generating ideas, it doesn't have to be a monologue delivered with no interaction at all. Pausing briefly after presenting your categories to check whether the interviewer wants you to go deeper on any particular bucket, or noting which category seems most promising based on anything mentioned earlier in the case, turns the exercise into more of a collaborative moment. Interviewers generally respond well to this kind of light engagement, since it mirrors how an actual brainstorming session with a client or colleague would naturally unfold.
Brainstorming when you have very little context about the company
Sometimes a brainstorm question arrives early in a case, before much detail about the specific company has been shared. In that situation, it's reasonable to briefly ask one clarifying question about the company's current position before diving in, since a brainstorm grounded in even a little real context will always be stronger than one built on pure guesswork about a company you know nothing about yet.
Transitioning smoothly out of a brainstorm and back into the case
Once you've presented your organized ideas, close the segment clearly rather than letting it trail off, a short line like 'those are the main directions I'd explore, happy to go deeper on any of them' signals you're done and hands control back to the interviewer. This small transition matters more than it seems, since an unclear ending can leave the interviewer unsure whether you're finished or simply paused, which can create an awkward beat before the case moves forward again.