0. Take GNOME Documentation Style Guide as a reference for style
Try not to get to bogged down being correctly styled. Hack on doco.
Make words. When you've got a bit of a groove happening start to make
your lives harder.
1. Open the project for the document About gNewSense
2. Propose a structure for the document (in any format)
3. Define the final structure from the proposals
4. Propose the content
5. Write a draft in the wiki combining the content proposals
6. Revise and improve
7. Write the final document in DocBook
7 is the step that worries me most out of those. If your going to be
doing that perhaps a script to automate wiki -> docbook would be in
order (one may exist already). Even if it just automates the basics,
its a lot better then a full rewrite.
The resultant docbook should probably wind up in a revision control
system of some sort as a 'step 8'.