Two words that can reduce a valiant warrior into a blob of jello. Query letter writing is the bane of the pre-agented author and it's almost as painful to talk about as to write them. But I'm going to give it a try.
Alright, so I'm no expert.
And I hate them.
BUT- I've gleaned a bit of helpful information which I will attempt to regurgitate for you now. Ahem.
First, a definition. A query letter is a single-page business letter introducing your novel (and yourself) to an agent or editor. It must sum up your story in one sentence plus one paragraph. (Explanation below).
Basics: Query letters are always written in 3rd person, present-tense POV. Always. Do not be "clever" by writing as the character or any such gimmick. In fact, leave all gimmicks at home. No colored paper, no perfume, no bribes or flattery. Do mention if you follow their blog or something, but don't blow smoke. Include the title, genre, and word-count of your manuscript. Address the agent by name, not "To whom it may concern".
Moving on now to the nitty gritty.
Query letters generally will always follow the accepted format of: Hook, Mini-synopsis, Bio.
Hook: An engaging one-sentence summary of your story. A sales handle. A promo sentence. A great tagline for your book. Call it what you will, it must "catch" the reader's attention and draw them further in to your letter, to the...
Mini-synopsis: In about 100 words you must summarize and sell your story. Sound hard? Of course it is. But 100 words or so is a whole lot more than you had to work with in the hook, so be grateful! Great writing is the most important thing here, this is your first impression.
Strong voice, show don't tell, all that jazz.
Important point! Query letters have to tell what your PLOT is. Not just describe your setting and characters. You must, must, must tell the agent what happens in your story. Include setting and characters of course, but action is most important. This is a common problem, as surprising as it sounds. So often queries go something like this:
In this really really cool Location, there are these amazing characters that came from This Place. He has never met someone like Her. She is really really funny and He is a hunk. When they meet, sparks fly. Wait till you read it! It's such a great story! Won't you be my agent?
What's the plot, what actually happens? Your query letter should jump right into the action from the get-go. A good formula to follow is:
When ____ happens, main character must ____ in order to ____ . But ____ will pose an obstacle. Character must choose to either ____ or ____ .
This is obviously not a fill-in-the-blank kind of thing. But you should get the idea. Start with the conflict, show what the character's goal is, what the obstacle is, what choice they have to make.
Conflict, Goal, Obstacle, Choice. Use your pretty words to beautify it, and off you go!
There are so many nuances to writing this part of your query, they could fill books- and they have! It's something you have to practice, and hone, and spend a myriad of time studying. Even then, it won't come easy. I've provided some excellent links for further study at the end of this article. Check them out when you have a decade to spare. Just kidding. But there is enough here to keep you busy for a long, long time.
Bio: OK, this should be easier than the last part but still not as much a cinch as you think. You have to be careful what you choose to include. You want to sound interesting, but don't drone on about yourchildhood in the 'hood, or brag about your multiple PhD's. Unless your novel takes place in the 'hood or your plot hinges on the latest bio-molecular-whatever-you-got-your-degree-in... leave it out. You can mention your love of animals but don't name each of your 20 guppies. Make sense? Bottom line, agents don't care about where you went to school or where you live or anything unless it has to do with your story. If you have previous writing credits, this obviously should be included. If you don't, just hush up. Don't announce that you're a noob.
One last thing. If you are submitting to multiple agents at the same time, you should mention that it is a simultaneous query.
So that's it in a nutshell. A small netshell. Like... a pistachio, not a walnut. There are tons of great resources out there to sift through, and lots more in-depth articles. Here are a few really good ones:
CBA Ramblings- How To Write A Query Letter(Rachel Gardner)
AgentQuery.com- How to Write a Query
Editorial Anonymous- Tips on Your Bio
Janet Reid- Effective Query Class
Nathan Bransford- The Anatomy of a Good Query Letter I
Nathan Bransford- The Anatomy of a Good Query Letter II
Nathan Bransford- The Basic Query Letter Formula
Public Query Slushpile (Have your query ripped to shreds for you)
Query Shark (More ripping and shredding)
**Feel free to jump in with further comments and points I failed to make, anecdotes, or just thank me for wonderful regurgitation. Mmm, yummy. =)