What is a query? A query is, essentially, a one-page letter sent to literary agents and designed to get them interested in a book enough to ask to see the whole manuscript. Hopefully, seeing the whole manuscript leads an agent to fall madly in love with the writer's work (and results in representation).
The letter includes such basics as the name of your manuscript, genre (young adult, picture book, etc.), a short synopsis, a personal bio of your previous work, contact info, etc. In many cases, if the query letter doesn’t pique an agent’s interest, a writer’s manuscript will likely never be read by that particular agent, regardless of how great the writing may be.
There is a process to follow. Every agent or editor looking for the next J.K. Rowling expects writers to follow whatever that agent's or editor's given submission process is. To the letter. Why lower the odds of a novel getting published simply by not following the rules? Crazy.
To raise the odds of a query leading to publication:
1. First and foremost - Check literary agency websites for exact, current submission guidelines. Follow guidelines to the letter, before pressing "send" on that query email. This cannot be stressed enough. Every agency has a website. Every agency posts submission guidelines. If a writer can't (or won't) follow the posted submission requirements, why would an agent think that writer will follow any guidance given once represented? A rule-breaker by nature? I'd say you are significantly lowering your odds of ever being published.
2. Spell the agent's name correctly. Check it, double check it, and triple check it. Enough said.
3. Only send your work to agents who actually represent what you write. Sending a middle grade manuscript to an agent who only handles adult fiction is a waste of both your time and the agent's. Know your audience. Spend the extra five minutes to google that person and see if they have a "wish list" of needs or wants. Read online agent interviews and/or check out the person's blog for a deeper understanding of whether or not your manuscript (and YOU) could be a possible fit.
4. Do NOT do anything cutesy to draw attention to your manuscript if sending in hard copy format via "snail mail" (a rarity with the online submission process most agents use). No, the agent will not think your query letter on pink, scented paper in an envelope filled with glitter confetti is clever. No, the agent will not think the homemade chocolate chunk cookies you included in the package make you the next bestselling "death by chocolate" author for their list. No, the agent will not think your use of comic sans font demonstrates the yuk yuk fest that is your romantic comedy set in upstate New York. No, no, and no. "But won't it help me stand out," you say? Please see #1.
5. ABSOLUTELY have a second set of eyes proof your query letter before you send it out to 20 of your favorite agents. Even the best self-editors can make a mistake or not see a problem with their own writing. Ask another person to read it for errors. With each manuscript, you usually only get one shot to impress an agent, and there are a limited number of agents to approach for any given project. Don't ruin your odds by being sloppy with your query letter. It is essentially your resume. That "resume" will end up in the "no" pile mighty quick if it includes spelling or grammatical errors. Agents will assume your manuscript is just as messy. That's a pass, almost always.
These are just a few pointers to help raise your odds during the query process. For info about how to write a query letter, check out one of my favorite resources, Jane Friedman's "The Complete Guide to Query Letters." I've also learned a ton by attending Society of Children's Book Writers and Illustrators (SCBWI) conferences, and I reference the "Guide to Literary Agents" and "Writer's Market," for the most up-to-date agent info. Most important - I don't send anything out until I've confirmed the submission guidelines online.
ALL of these efforts take me one step closer to my goal. Raise your odds. Follow the process. And good luck!