Dear Fiction Editor: I am writing to respectfully withdraw my story from your consideration, as submitted on [date in 2007], about [number >8] months ago. The story has been accepted elsewhere for publication. I have a sense that it matters very little to you, but I thought I'd be polite anyway and get in touch to let you know. Thanks so much.
Best, Writer, Rejected
As you can see I'm geting saucy.