I came across this post about categorizing your manuscript in the query letter and it made laugh, since it definitely makes me think of things I've seen while reading the slush pile at my internship. Especially when she talks about the mistake of categorizing your manuscript too specifically. My fellow intern once read a query that said their work had fifteen genres. I also agree with her about having "killer pitch" and "tight, great polished writing in the actual ms." Regardless of genre, we all just want to read something that piques our interest and is also well-written.
She's also right about it not being true that agents just reject queries because of minor formatting issues or because you categorized your manuscript "incorrectly." Believe me, I have gone on to read the sample pages from queries that had more than just formatting problems wrong with them. Unless you sound like a stark raving lunatic in your query letter, I will probably read your sample pages. To me, I'd rather read a short and to the point query letter with a couple of typos than a novella length query - at that point, I feel I've invested all the time in your work that I can possibly afford.
"Agents are just people. People who love books, and who want to help facilitate the making of books. People whose job it is to advocate for authors."
This is so true! Like in any profession, I know there are agents out there who aren't the best, but the ones I work with truly love their authors and work really hard to sell their books all across the globe, to play hardball and get them the best possible deals, and most of all, they love discussing their authors' manuscripts around the office.
My basic, basic tips on querying fiction would be to read the jacket copy on every book you come across. Make a note of what works and what doesn't. When I read your query, I should know who the main characters are, what the inciting action is, and what complications will arise over the course of the novel.
So get out there and send out well-written queries, authors! And please have someone read it over. Writing is a passion, but getting published is a career, and you need to be professional. You wouldn't send out a cover letter without looking it over ten times; the same should be true of your query letter. Good luck!