Many writers tend to focus on their manuscripts and dismiss the query letter as a mere formality. In fact, the query letter is the most important piece you'll write because it's the only piece guaranteed to be read by an agent or an editor — or at least by their assistants, who often have the authority to accept or reject. A poorly written query will get you a quick trip to the dead file. A well-written, well-presented query makes you look professional and knowledgeable, a promising candidate for publication.