Group brainstorms don’t work. A Google exec says this is a far better approach –
The big idea of the sprint is to take a small team, clear the schedule for a week, and rapidly progress from problem to tested solution. On Monday, you make a map of the problem. On Tuesday, each individual sketches solutions. On Wednesday, you decide which sketches are strongest. On Thursday, you build realistic a prototype. And on Friday, you test that prototype with five target customers. It’s like fast-forwarding into the future to see your finished product in the market.