Plan your query before you write it. The primary goal of a query is to have an answer to one or more questions. If you're writing a query to an editor at a publishing house regarding a manuscript you would like him to look at, your essential question will be: "Are you interested in looking at my manuscript?" This is the focus of your letter, but it would be rude to send a letter that does nothing more than ask this question. You need to decide what comes before the question.
Compose a brief introduction. Tell the editor who you are and give a brief overview of any previous publishing credits you have. If your previous credits are numerous and you want to include many of them, consider including a short bio separate from the query letter itself. If your query is to a company regarding a product, your introduction might state how you heard about the company and if you're an existing customer. Regardless of the subject of the query, the structure remains the same.
State the purpose of your query. Tell the editor you have a manuscript you would like him to consider for publication. Give a brief synopsis (no more than a paragraph) of the story, state the word count and ask permission to send the manuscript for the editor's consideration.
Close by thanking the editor for considering your query. Be sure to include your complete contact information, including phone number, street address and email address. Your query should not be longer than a page.
Verify the address and the name of the query letter recipient by calling the company ahead of time and asking. Make sure your letter is dated and that the address of the contact and publishing house is in the upper left side of the paper under the date and right before the salutation.