1. Choose Your Players
Typically, people are less apt to suggest bold, unconventional ideas in front of direct superiors. If you're a boss, select a neutral party, ideally a professional facilitator, to lead your brainstorming session. (If you can't hire a pro, at least recruit someone from another team or department.)
Assign one participant to record ideas, and make sure he or she knows to write down everything, even the duds. In addition to core members of your team, invite guests from other parts of your company — outside perspectives often help spark unexpected ideas. The total group should number no more than 12. (Big groups allow participants to hide in the background, and you'll run out of time to hear all ideas.)
2. Assign Pre-meeting Homework
Precious meeting time can easily be wasted getting people up to speed. Meanwhile, good ideas don't come out of nowhere — they're often the product of focused attention and mental struggle. When you first invite participants to the session, tell them the one problem you want to solve and provide any relevant background. This is also a good time to set the ground rules of the meeting (i.e., no critical comments). Tell attendees you'd like them to show up with three ideas, to ensure they will think about the problem ahead of time.
3. Don't Tolerate Criticism
One of the most important rules is to require everyone to withhold comments and reactions to each other's ideas. Even an eye roll can stifle creativity: if people are worried that others are judging their ideas, they'll probably just keep their mouths shut. Remain open to even the most outrageous — or stupidest — ideas. An offbeat remark might end up triggering a good suggestion from someone else.
4. Encourage Collaboration
Lead participants to build on each others' ideas with a sense of collective momentum. Focus on quantity, not quality, with comments like, "Wow, we've got 40 ideas. Let's see if we can get to 50." Toward the end of the meeting, when there's a lull in the idea generation, encourage people to see if they can combine ideas in order to improve them.
5. Evaluate Later
Postpone any criticism or weeding out of ideas to the end of the session (or even to a later meeting). Because evaluating ideas and generating ideas are two different brain functions, people can't easily switch between the two. In other words, creative thinking ability shuts down the minute you start analyzing.
6. Don't Get Discouraged
Brainstorming sessions are a form of exercise: it takes time to get in shape. If your first meeting doesn't generate many ideas, consider it a practice run. Brainstorming isn't about any one meeting but the rigorous practice of increasing your team's problem-solving capacity over time.