Let’s begin by pointing out something very important: brainstorming is not project management, nor is brainstorming anything more than a “tool”.
Is brainstorming a tool?
Brainstorming is just another name for open discussion: nothing more, nothing less.
Now, everyone can’t but agree on this point: discussion is fundamental, provided … it is positive discussion, i.e., people are focused on the matter.
Unfortunately, in recent times brainstorming has become a synonym for chatter: that is not the right way.
Let’s speak about positive brainstorming.
To begin with, the project manager should indicate the factors to be discussed.
Then, he/she ought to make clear everyone should keep to the matters under discussion and stay focused – brainstorming is one thing, speaking of things with no relationship to the matters under discussion is another one.
After that, the Project Manager should be ready to correct “deviations”, i.e., the very enemy of brainstorming.
Look, all this is easy: think of the rules usually applied in successful meetings and apply them.
All this is especially important while dealing with projects.
Brainstorming is very useful, especially in the first phases of a project or in case of technical problems, but … it also can be the end of a project.
Remember: brainstorming is solely an aid to the project manager; never ever forget that brainstorming (used) alone is going to lead your projects to disaster.