7 Secrets of Better Brainstorming

1: Sharpen the Focus:
Start with a well-honed statement of the problem.

2: Playful Rules:
Don't start to critisize or debate and encourage wild ideas.

3: Number Your Ideas
Go for quantity - 100 ideas per hours is good!

4: Build and Jump
When the energy starts to fade, a facilitator should build on an idea or take a jump.

5: The Space Remembers
Capture the ideas in a medium visible to the whole group.

6: Stretch Your Mental Muscles
Warm up if the group are new to each other or don't regularly brainstorm or likely to be distracted by other pressing matters.

7. Get Physical
Encourage diagrams, stick figures, mock-ups and models.

Reference:
http://www.masternewmedia.org/news/2008/03/14/effective_brainstorming_7_tips_to.htm