Why this is a mistake: Query letters are sales tools. Plain and simple. To hook an agent or editor into taking a look at your manuscript or article, you have to write a great query letter. If your topic or storyline is muddled and ambiguous, then the acquiring agent or editor is going to assume that your manuscript will be as well.
The solution: The first line of your one-page query letter must grab the reader, because it is the first (and maybe the last) line the person opening your submission will read. Next, grab the agent’s or editor’s interest with a paragraph on your book or article. Remember to include some factual information like: “This is an 85,000-word sci-fi novel,” or “‘Ten Tips for Off-Roading’ is a 2,000-word article.”
In addition to a sales pitch for your manuscript, you need to include a sales pitch for yourself. The manuscript is an extension of you. What special background do you have that would make the editor want to see what you have done? This means not only any writing background you have, but also your background as far as the story goes. This does not mean you won’t get looked at it if your background doesn’t have much direct application to your subject matter and you have little writing experience, but editors and agents also remember what Mark Twain said: “Write what you know.” If your job or background in any way applies to what you’ve written, make sure you mention that.