One of my favorite parts is the interactive quiz called “Is Your Manuscript Dead on Arrival?” In about five minutes, it shows you if your MS has any red flags that might turn off an agent/editor. It consists of questions like are characters being hidden royalty/family/part of a great prophecy, is the dialogue like reading a transcript, and do you overuse made up words/obscenities.
The site even has a post on writing queries called 16 Reasons Your Manuscript Got Rejected Before Page 1. Besides listing the usual be courteous, use-the-name-of-the-agent type advice, he explains why insisting your book is the next Harry Potter is wrong and what details are important--like the actual plot, not just a fanciful description of the world you created. Confused about credentials? He tells you what’s important and what will make an agent think “Like that matters.”
And this is only a small sampling of what the site has to offer. There are articles on avoiding dialogue mistakes, writing the dreaded query and synopsis, writing action scenes (very useful for me), how to write comedy, and writing male characters--super helpful for me as a female writer. Learning about the subtle differences between how males and females think really got me into my MC's head and helped me create realistic sixteen-year old.
In all, Superhero Nation is a a great resource. Check it out. With all they have, you're bound to find something. I know I'm going back as soon as I hit Publish Post.