These are SO important. I've found that groups where we've stuck to these rules have worked way better than those where we haven't. In fact, I highly recommend writing them on a sheet of paper and sticking it on a wall while you're brainstorming. I've even done this in cafes.
Some things I've learned about brainstorming: make sure your team knows when it's brainstorming and when it's narrowing down and constructively criticizing. If some members think you're doing one, and some think you're doing the other, there will be problems. Designate one person as the facilitator and one as the recorder, and take turns performing these roles. Finally, DON'T STOP BRAINSTORMING after you've come up with your first prototype! Each redesign should be a new brainstorm--and don't be afraid if you start to go off in a new direction. If you're going there based on feedback, a new direction is probably a good thing.
Coincidentally, these rules could be pretty helpful for learners to follow in any group (especially project-based) learning situation, as well...
Hey, if I write these here, I won't have to carry tape around with me all the time anymore.