So, you’ve decided that you want to go about publishing the old-fashioned way. The first thing that you need (besides an amazing piece of writing) is an agent. And to get one of those, you’ll need a query letter.
A query letter is like a pitch — in around 300 words, you need to convince a literary agent that your manuscript is worth their time. Put as much effort into the letter as you did into your writing itself, because it’s just as important.
First things first, be sure to address the agent by name (and do your research beforehand!). Don’t send your query letter to every email address that you can find. Look into agents who specialize in your specific genre, and look into their individualized submission guidelines. Do they want your query letter sent hard-copy through the mail or through email? Do they want a short portion of the work attached? Almost assuredly they’ll you know on their website if you do a little digging.
Keep it under one page, and don’t do anything too crazy. Keep your greetings formal, your fonts standard, and your sentences simple and clear. Start with a tasteful hook, if it feels right. Share the title, genre, and word count of your book right off the bat. Then explain why you’re sending your query letter to this agent specifically.
After the introduction, start summarizing your work. Describe the main characters, setting, and conflict — don’t give the entire plot away, but try to draw the agent in with some sort of a cliffhanger. Again, keep the wording clear and straightforward (but still well-written, of course). Agents are reading tons of these at a time, so make it easy to skim, yet interesting. Hint at obstacles the protagonist faces or changes they go through. You could even mention the tone of the book or make comparisons to similar authors or novels. Then, end with a couple sentences of relevant writing experience or a short bio. Don’t be afraid to get personal, but only if it helps to further explain your work or your credibility. Literary agents don’t need to know about your pet chihuahua if you’re submitting a manuscript about the Civil War, for example. But if it’s a story about said chihuahua, it might be a good idea to mention it.
Writer’s Digest has a whole section (here) where they print the query letters of books that were successfully published. Sample query letters are a great way to get ideas and inspiration for your own! Good luck!