As I began writing to one student about game design and a role mind mapping might play in the process, I realized I hadn't said anything about mind mapping when I discussed pre-writing. Mind mapping is an all in one tool for pre-writing. It can take you from brainstorming ideas, through research, into organization, and even early drafting. You can then use the word processor and cut and paste from the mind map into a text document, hyper-text dcument, etc. to bring your ideas together. In any event, here's my response to the student:
There's one particular concept which helps many students move between the unorganized step of coming up with ideas to a more organized outline. I don't know if you are familiar with mind mapping. Essentially, a mind map is a set of bubbles connected with lines. When brainstorming, one starts with a topic in the center bubble and adds other bubbles as ideas occur. I used to study for tests using mindmaps drawn on blackboards at college, creating mind maps for each concept or term I needed to understand.
I also used the technique in coding. I would have the central thing the program was to do as the center bubble, and I'd begin my brainstorming for ideas by adding sections of code I knew needed to be in the program. As an algorithm would begin to emerge, I'd move the various sections around until I had them in an order which worked. The map, hence, served as a place to brainstorm, as a way to note sections of code I needed, as a place to store stray thoughts, as a place to take notes, as a means of trying out different ways to order these sections of code, and a way of organizing the program as I went. A similar process might work for the stage of game design where you are developing ideas and working toward an order.
There are a host of good mind mapping programs out there. There's a free, open source version called FreeMind. There's a payed version call Mind Manager, and there are online, collaborative versions at sites like bubbl.us and mindmeister. There are also a host of good blogs and forums which will explain how to use mind maps as a brainstorming or organization tools.
What I liked about mind mapping and the reason I recommend it to students is it's a good way to move between a good idea, brainstorming how to develop the idea, research, and organization all using a single place and using a single method. Organization is accomplished by ordering the nodes in your map clockwise: first to last, most important to least, etc. I also like that mindmap programs allow you to accumulate a lot of information in one place. If I might use a website or an article to develop an idea, then I include a link in a node under that idea. If I end up pulling out invidual quotes, then I just put them in their own node. I can also create the text connected to an idea and save it as a sub-node of the node I created for the original idea. This last allows me the fexibility to play with orgranization up until I put the formal text together using cut and paste and a word processor.
You also might want to look at Writer's Blocks. I know a number of folks in Hollywood use blocking or story-boarding in developing ideas for film. A simular method might work with game design.