You know the ritual. Eight people at a table, sticky notes, a flip chart, someone says 'there are no wrong ideas'. Two hours later the wall is covered in coloured notes and everyone goes home with the feeling: we did something. The week after, nobody remembers what was come up with. This is what creative brainstorming for an event too often looks like.
Most brainstorms fail because they start without direction. People come up with loose things (a magician, an escape room, an act from years ago), without anyone asking the question of what they're working towards.
A good brainstorm doesn't start with ideas, but with a question sharp enough to be able to say 'no'. 'What could we do at our staff party?' isn't a question. 'How do we celebrate having a grip on things again after two tough years, without it feeling like a victory party?' That's a question that prompts answers that mean something.
