One of the easiest ways to learn what makes a good, standard query letter is simply to see an example of one that does its job well. If you write fiction or narrative nonfiction, a query letter is your first (and often, your only) chance to get an agent interested in reading (and, with hope, signing) your work. You should put just as much care and attention into crafting and polishing your query as you did into your manuscript. After all, if your pitch doesn't hit its mark, your book will never leave your desktop.
The main objective of a query is simple: Make the agent care enough about your protagonist and your plot that she wants to read more.
Following is a successful query for a middle-grade novel that led to me first requesting this full manuscript and later signing on to represent the author, Dianna Dorisi Winget. Her debut book, A Smidgen of Sky, went on to sell to Harcourt and hits shelves this fall.
No matter what you're writing-fantasy, thriller, sci-fi, romance-or whether you're writing for children or adults, there's a lot you can learn from this example about conveying characters clearly and getting an agent invested in your story in just one short page.
-by Mary Kole, literary agent
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Example of a Query Letter
Dear Ms. Kole,
According to your agency's website you're actively seeking middle-grade fiction, so I'm pleased to introduce my novel, A Smidgen of Sky.  This novel won me a scholarship to attend the Highlights Foundation Writers Workshop at Chautauqua. It was also awarded honorable mention in the Smart Writers W.I.N. Competition.
 A Smidgen of Sky is the story of ten-year-old Piper Lee DeLuna, a spunky, impulsive dreamer, whose fierce devotion to her missing father is threatened by her mother's upcoming remarriage.
Everyone else has long accepted her father's death, but the fact that his body was never recovered from his wrecked plane leads to Piper's dream that he might one day reappear and free her from the secret guilt she harbors over his accident. Her stubborn focus leaves no room in her affections for her mother's fiancé, Ben, or his princess-like daughter, Ginger.
Determined to stop the wedding, Piper Lee schemes up "Operation Finding Tina"-a sure plan to locate Ben's ex-wife and get the two of them back together. But just as Piper succeeds with step one of her plan, a riot breaks out at the prison where Ben works, and suddenly nothing seems sure.
 Since middle-graders care deeply about things and people and love to daydream about their future, I think readers will identify with Piper Lee and find her an appealing heroine as she learns that you can both cherish the past and embrace the future.
 This story, set in the coastal region of Georgia, runs about 33,000 words and is somewhat similar in tone to Kate DiCamillo's Because of Winn-Dixie.
 I'm a 1990 graduate of the Institute of Children's Literature and my work has been published in U*S* Kids, Child Life, Columbia Kids, True Love, Guide and StoryPlus.
Thanks very much for your time. I have included the first ten pages and look forward to hearing from you.