Not really. There's the editing help page (it's linked on the front page as well as at the bottom of the page whenever you edit something) and that tells you how to format and how to organize the article you're writing, but there's nothing about how to organize the whole wiki.
Really, the best way to organize everything is to make sure you put what you write in the appropriate category and include links to pertinent pages. Like if a "How to fix a Jawa" article did get written, it should have a link on the Jawa page that you started. (And of course, it would also be categorized into the Repair tutorials category and anywhere else that made sense). Then if people are looking for information about Jawas, it'll all be linked right there on that one page.
If there are a lot of articles about something, then they probably need their own category (like the Puch stuff), but it doesn't really make sense for each brand to have its own category until it's got 10-12 separate pages related to the brand (--in my opinion, anyway).