Scott Berkun shares some great tips and tricks on How to Run a Brainstorming Meeting.  The entire article is worth a read, but I especially liked his tips to get a group unstuck:

What is the opposite of what we want? Get the group to describe, in detail, the opposite of what you want to have happen. What’s the worst web navigation design possible? This never fails to get people to smile, and dig in. It’s just so much fun to work the other way for once. The trick here is that before people know it, they’re sharing ideas, being clever, and communicating well. At the peak of momentum, shift gears the other way. “Ok. We have a horrible design. How do we achieve the opposite of this?” You’ll be surprised at how original some of the ideas that follow will be.

Random theme generators: (This works only for design related brainstorming) Before the meeting, make a big list of adjectives, colors, verbs, and attributes that might or might not apply to the project (20 or 30 of each). Write them on index cards, but keep them in stacks. Shuffle each stack. Then pick one from each, and try to design something for it. “Agile blue focused”. What features would a car/website/software/sneaker with these attributes have? Or go through the list of adjectives and verbs and get the group to pick the ones that are most interesting in relation to the problem at hand. Papernak’s Design for the real world has a set of these, but there are similar kits you can buy (Anyone know of other kits? This was the only one I could find. Let me know if you recommend others.)

Rotate: Anyone, at any time, can call out “rotate” and everyone in the room has to get up from where they are sitting, and move to the chair to their left. I have no evidence to prove it, but I’m convinced moving around physically helps people to move around mentally. It’s usually the facilitator that calls this out when people get stuck, or the energy doesn’t feel right. Bonus points for getting people to do the hokie pokie (a stupid childhood dance) or something silly that makes them laugh and let down their guard.

Roadblock removal: Eliminate assumed constraints. Tell the group there is no limit on costs, or time, or other resources. They can think as big or expensive as their minds allow. Think of other constraints that the group is assuming. Business? Political? Customer? Take the biggest ones you can find and get rid of them. Removing a roadblock might free new directions of ideas that wouldn’t have been considered otherwise.

Roadblock introduction: Come up with some ridiculous new constraint to the problem. The goal isn’t to make it harder, just to force people’s creative muscles to work differently. Suggest that everyone that uses the product will be right handed, or that the website can only work in Arabic (or some other non-Western language). Make the problem as difficult as possible: pretend the budget for the project has to be $50 or less, or that instead of the 2 months to write specifications, there are only 2 days. Don’t let people cop-out: push them to work with the problem. This can often shake people up into action, challenged by the insanity of the problem, and protected by the feeling that since it’s a ridiculous situation, there are no bad answers. Guaranteed they be stretched creatively, find new ways of thinking about the work, and will be relieved or energized to return to the real constraints.

What are your best brainstorming tips?