A reader writes to ask:
I am going to FEDEX my short fiction story to [a certain American] magazine, who were the only gracious ones to send me a response to my e-mail query (out of hundreds of e-mail queries sent). Before i do that, i need to enclose a cover letter with it. Would you have a sample i could use?
That's a bit outside the scope of this blog, but since it does have to do with the image of yourself as a professional writer that you present to an editor, I'll judge it a fair question for consideration here.
A cover letter should almost always be short, simple, and to the point. What it contains will be different depending on the circumstances of your submission.