Wrote a new resource (aimed at students/hobbyists/beginning devs) for writing GDDs that are useful! I had a lot of advice from the good folks here at Cohost for this one (several are quoted), as well as a LOT of GDC talks and Game Developer blogs etc. It's all mixed in with practice from my own teaching + design stuff.
The BIG TAKEAWAY of course is that GDDs are NOT not a monolithic format -- docs can take many many forms and should be very clear, concise communication tools, not long-ass design bibles that only the designer will ever read. I was also keen to include perspectives from designers who do not use them or find them helpful, so new devs know that any team they might work with may have very different methodologies for communicating design.