Double spaced is industry standard if you're talking about a manuscript that you'll be submitting to publishers. For more guidelines see: [Shunn.net][1] [Writersdigest.com][2] [1]: http://www.shunn.net/format/story.html [2]: http://www.writersdigest.com/online-editor/what-are-the-guidelines-for-formating-a-manuscript