Two rules you need to bear in mind: 1. Keep it simple. 2. Keep it brief.
My basic query idea applies whether you write to agents or editors.
I suggest you write one paragraph that gives them your idea for a book or an article. Call it the elevator pitch, précis statement, or concept (the term I use). Don't give them a sales pitch such as, "This book will revolutionize the way people eat cereal."
In the second paragraph tell them about yourself. Give them your background, education, experience, your work or profession—anything that shows your credentials to write the article or book.
Your next paragraph reads: May I send you my article? If it's a book, you ask to send your book proposal. If you have completed your manuscript, you write: May I send you my proposal or my completed manuscript?
Query letters are simple sales pitches. Make no claims for what your article or book will do. Just tell them what it is.
A query letter is a business letter.
It asks an editor to buy your product.
And the editor probably knows the product better than you do.
A note from Twila: Would you like to spend some time with Cec on a cruise to Mexico? Check out the Sailing Toward Success Christian Writer's Cruise. Cec is the keynote speaker and one of the instructors. The cruise dates are February 27-March 6. If you choose to go, please send me a postcard so I can share in your experience. Because I'm such a faithful, hardworking (and humble) employee, I'll stay behind to keep the empire running. But that's okay--anything for Cec. :-)