I like step 4: "Test your ideas: this is where most brainstorming sessions fail to take the one extra but necessary step. Instead of selecting your ideas on the spot, you need to test them in the real world. Select the few most promising candidates, and see how your audience reacts. For a book, write a blog post. For an app, build a landing page or a quick MVP."
I had many brainstorms resulting in a long list of unproven / untested ideas.