We're living right now in the age of reason and this often makes us often forget that rationality is but one side of our mind. Using a single tool to solve all possible problems can prove sometimes restrictive, other times simply impossible.
That's why some people try to prove brainstorming ineffective: it doesn't quite fit with the logical part of our brains. They are partially right: brainstormings have nothing to do with rationality, they have everything to do with imagination. As long as they try to go through them using only the rational, they will fail. Reason can only set the goal of the brainstorming session. Reaching it it's a job for the other side of our minds.
There's more than one reason why rationality shouldn't be allowed at the brainstorming table:
First, it has nothing new to bring here. Reason is the product of our past experiences. It can reverse engineer what others did, it can judge, it can infer or deduce. But it doesn't invent new ideas. That could be why so many things these days are just copies of copies of copies.
The second reason is exactly it's judging function. Imagination works best when mind it's in an open state. When it achieves a flow where it freely associates, transforms and combines new elements. The more fragmented by judgment this process is, the less efficient it becomes.
Instead of letting the imagination roam free, rationality pins it down after each discovered idea.
Reason wants to limit the number of elements on the table, because the more elements, the more complex the processing becomes. Imagination just thrives in new ideas. Reason creates rules. Imagination breaks them.
If reason should be allowed to interfere here is just to steer the discussion back to the goals, if they get left behind in the conversation.
Brainstorming worked fine for me and for other people I know. I see no reason why it shouldn't work for you. Just let the imagination fly. And whenever reason comes uninvited, kick its teeth in.
The immediate result should be brainstorming sessions that end in a lot more ideas then before. Sometimes a good crop of ideas if everything you need to start on a good project.
2. Idea selection
Making a game is like completing a puzzle nobody has ever seen, whose pieces you invent one by one. Only instead of actual pieces you use your ideas.
Reason shouldn't interfere with creating these ideas, but once gathered they shouldn't just stay congregated in a big pile. To be turned into a game they need first to be interrogated, selected and organized. This is a job for the rational side.
Each of them needs to answer a set of questions: Does this idea fit the game? Does it make it better? Does it fit with all the other ides?
After the first session of questions, the ideas that qualified will need to endure a new one: Will these ideas fit into the time and budget? Will the programmer chase me with a fire axe when he finds out about them? Are these ideas worth being chased for?
Once the ideas proper for the game are selected, I usually choose 3 or 4 of the bigger ones to be the spine of the game and use them to push the device I'm working with to the upper limit. The they will feature prominently in the first pitch, they are soul of the game.
What I would insist on during this phase: keep your emotional part out when judging your ideas. Because emotion harbours your biggest enemies: love and fear.
THE GREATEST MISTAKE A DESIGNER CAN DO IS TO FALL IN LOVE WITH HIS OWN IDEAS!
Never do that. Because you should always be capable of understanding what advantages and disadvantages they bring in. You must know where they fit and, most importantly, why they fit there. You must be able to kill them, if they get too cocky and try to take over.
Your ideas are tools to be used to improve your game. They are not here to make you look smart or sound important. You need to learn how to get the ego out of the goddamn way.
THE SECOND GREATEST MISTAKE A DESIGNER CAN DO IS FEAR FAILURE!
At the other extreme, you can't create a good game discarding everything new or cool or spectacular because it might be hard to implement. At some point you will need to ask for time and trust to experiment and fail until you get it right.
Now is a good moment take a step back and look at what ideas you selected. Are they inspiring you? Is it there something people will find exciting and fun?
Reason can't tell you how to feel about your game. If after gathering all these ideas you are not convinced you're creating an extraordinary experience, you'll never be able to convince others.
It's the role of the designer to inspire the team and convince the powers that be that these concepts can achieve greatly.
If you feel you can't do that with you gathered so far it's time to go back to the drawing board.
4. Specifications and feedback
In order to make a game you need to know what it is made off. Once the game ideas are deemed good enough, it's time to shift from concepts to game elements. They can be characters, items, opponents... everything in your game that can interact with the player.
These elements must be described in the most clear, simple and comprehensive manner. The artists and animators will need to know how do they look like and how they move. The programmes will need to know how they behave and how they relate to the other elements.
This is a job for the left side for your mind: the better presented and organized this information is, the better the project will go.
When these people will have something to show you, it's time to tell them if that's what you wanted, or, if not, what's wrong with it. Again, this must be explained in the most clear and concise way.
And there is, of course, the matter of receiving feedback from someone higher in the food-chain. I’ve seen two kinds of wrong approaches here:
One is taking the feedback as it is: they are the bosses, so they must know what they’re talking about. This one usually disempowers you.
The other is the exact opposite: how dare they ask to change my beautiful perfect game? Bastardos! This one usually gets you fired.
Instead, each item of the feedback must be interrogated on its own, in the most rational and honest manner:
Does it benefit the game? Yes? Hey, what do you know, they really understand what they’re talking about, these feedback guys!
It doesn't benefit, nor hurt the game or the volume of work? Cool, let's do it, since they sign our bloody paychecks.
Does it hurt the game quality, or throw everyone in a draconian crunch? You sure? Remember: no love for your pet ideas, no fear of failure. If it does, this is another step where you shouldn't start getting emotional. No, it is time to start negotiating: What are the strengths of the ideas you decided to defend here? Why do they want them changed? Can you offer alternative solutions that would keep everyone happy? Can you provide examples of successful games that use ideas similar to yours?
One last thing you must remember: when negotiating, you need a bargaining chip. To paraphrase the cinema expression: You are only as good as your last build was. If your last build was weak, your next proposals will be regarded as such. If you maniacally added quality and high production values to what you've shown, you will have more success in your negotiation.