In his book, The Creative Shift, Andrew Robertson, Chairman of advertising giant BBDO, gives this succinct guidance for brainstorms and idea meetings:
Go Wide, Go Narrow, Go Deep, Go Public.
Go Wide. Use divergent thinking to generate a great number of ideas including absurd and silly ideas. No criticism or judgement allowed at this stage.
Go Narrow. Sift the ideas down to a shortlist using some agreed criteria. Shape bizarre ideas into creative, workable proposals. Select the best few.
Go Deep. Examine in detail the handful of promising ideas. What resources and approvals do they need? How could we test them quickly and cheaply?
Go Public. Take your selected ideas and plans to those with authority to approve them. Gain permission and resources to test them.
Good advice.