The best way to convince a publication to purchase an article from you is to offer them something new and interesting. If you pitch them an article that sounds similar to a previous article in their publication, or something similar that ran in a rival publication, you probably aren’t going to make the sale. Most publications aren’t in the business of repeating the same material over and over again.
It can be difficult to come up with truly original ideas, especially when you are dealing with a publication that caters to a narrow topic. A magazine about model trains or a web site about search engine optimization doesn’t have much new ground to cover after a while. Still, if you consider yourself a knowledgeable writer about one of those subjects, you should be able to find a fresh approach to the material. You may not come up with an idea that has never been used before, but at least try to find a new way to present the material. Often, it is a good idea to get more specific. There may be many search engine optimization articles about using keywords, but if you take the time to discuss a small part of a specific technique, you might find some ground that has not been covered.
When you do have a new idea, or a new take on the subject, make sure that you emphasize that early in your query letter. The fact that you aren’t offering the same old story should be one of your key selling points in your query letter. Your goal is to stand apart from everyone else. It is worth spending a little extra time thinking about how to make your idea original. Another good way to do this is to add a little personal experience to your pitch or to pick an overriding metaphor that hasn’t been used before, such as comparing model train enthusiasts to politicians. No matter how you go about it, find something new to say if you want to make a sale.