Really, honestly, truly, if you are submitting fiction (or non-fiction) anywhere for any market, follow the submission guidelines as given on the publication’s, publisher’s, agent’s, or editor’s site, to the letter. Otherwise it becomes an excuse to throw your work away without reading it and why give anyone a free excuse? Submissions are flooded and everyone is looking for a way to cull the slush as quickly as possible. Don’t let your work be the garbage that’s easy to throw away. Force the slush readers to be creative about throwing your stuff out–they might discover that they like it if they have no excuse to toss it first. Yes, there are exceptions to every rule, but you’ll raise the odds in your favor if you don’t have to be that exception–especially on the days no one has time to make you the exception. It’s not hard to find the guidelines, and in this day of electronic submissions, it takes very little time to reformat a document or compile a different number of words to suit a requirement. Also, personalize your cover letters–proof that you did some research and took the extra step is worth it. This I give you for free, because as a former (and possibly future) editor, I appreciate this. As a workshop leader, I appreciate this. As an author I appreciate that my agent, editor, and publisher are my partners in making my work successful.
(Edit: Also, don’t submit something inappropriate or outside of the genre/submission call/etc. Your work will be 86ed faster than rotten fruit if you send something that doesn’t fit to begin with.)