The two most essential places (Score 1)

The most complete guide is on the International Game Developers site http://www.igda.org/biz/submission_guide.php (free reg req.) That's an industry standard. Also, Sloperama.com is perhaps the best resource on the web for game submission techniques and requirements for game jobs. He is a 30+ year expert in the field and deals with your question specifically with GDD examples and everything else.