The best brainstorming sessions are traditional ones, with a wide variety of people coming together to throw ideas out with no judgment on even the craziest notions in the first phase.
These take time, dedication, and a willing and able group. But, for a writer flying solo and pressed by one of those nagging problems manuscripts seem to invent as obstacles, traditional brainstorming may not be available. Can you approach the level of creativity and openness of the original?
Preparation is needed:
Step 1: Frame some good questions about the problem. Write a lot of questions down. The first will be direct, but keep writing until they get weird. I had a story once where the main character alluded to a disaster caused by an employee through most of the story. I had not idea what this disaster was, but I knew it would be an unintended consequence of another character trying to achieve a cherished goal.
Q1: What was the disaster? Q2: How could the employee achieving his goal (winning the love of a colleague) cause problems for anyone? Q3: How does love upset the status quo? Q4: How does the employee need to change to reach his goal? Q4: How does that change affect what the main character needs from the employee?
And so on. By the time I got to Q20 (without having generated any answers to the earlier questions), I was asking what crime the main character had committed to break up the lovers. And I already had the outlines in my head of a peculiar world with crimes that make sense there, but not in our world.
Step 2: Once you have two or three bizarre questions, get moving around physically. It's okay to think about the questions, but it's not necessary. The important thing is to get your blood flowing and to step away from what is bothering you.
Followed by determined action:
Step 3: Don't sit down. Go to a white board or a flip chart or just take a grease pencil to a shower stall wall and start writing down answers to the questions. No filter. You can write single words or full sentences, but you can't stop until you have 50 words written down. Even better, make it 100.
Step 4: Expand on each idea so each is in a full sentence. Don't leave any of your words behind even if they seem stupid. Expand as you will on the best ideas, but avoid the most conventional. I often do this by talking about the ideas (using a dictation program, but recording works fine, too).
Step 5: Force rank at least five ideas. If you are on a tight deadline, pick a favorite and put it to work in your story. If not, leave your choice for tomorrow.
That's it. The whole process for me takes about two hours. It takes a little longer if I have already written a scene since it's harder to force the failed images and ideas (and the emotions they create) out of my head.
Oh, and if you wait to the next day and an even better idea comes to mind? Use it. That's what happened to me in the example story. I sat down to use my top idea, and it was immediately forced by a solution that demanded my attention. And I was delighted with the results.