We have already explored defining and communicating game ideas to others through the game concept document, now let's pose a more fundamental question. How do we generate the game idea in the first place? How do we get to the point of having something to write down in the concept document?
Before we begin, let's make it clear that the game designer is not the ideas guy. It is not their job to have a constant flow of new game ideas. These can (and should) come from anyone in the company or even from people outside your organization. It's very common in our industry to have publishers commission a game idea to the developers, an owner of an intellectual property (IP) such as Star Wars or The Witcher to seek out licensing, or game studios themselves providing outsourcing services to other developers.
A game idea could be driven by market research, a game vision, or even, in a more artistic way, by the urge to say something or tell a story. What is really important for you...