Productive Brainstorming Requires that you Separate Creative Thinking from Critical Thinking
I had first hand experience of this productive brainstorming at the weekend when I was collecting some ideas for a journalling application. The problem was that each idea I had was quickly followed through by my more critical side asking "How would that work?". As soon as I had an idea I would quickly invalidate it by thinking that it would be too difficult to implement. You're not going to get any ideas by doing this.
Looking back I should have simply put my ideas down first without giving them a second thought about how they would be implemented and then let them incubate.I do this quite a lot with a blog on mind mapping, but it's something that I had forgotten about at the weekend when I was trying to be creative and generate some ideas.Let your ideas grow in your mind for a while before applying the critical thinking to them.
I would recommend at least a few hours or even a couple of days between creative thinking and critical thinking.The time when your ideas are in an incubation period can give you a chance to reflect on your ideas. This isn't time when you should be thinking about the critical aspect of your ideas, instead it's just a time for the ideas you have, to sit and do nothing.While they're doing nothing you might trigger a thought to a more refined idea. Then again you might not.
You don't lose anything here but it does mean that when it comes to the critical evaluation of your ideas, you'll be familiar with each of the ideas you originally had and you'll be ready to apply some critical thinking to them.