Just doing my monthly markets' column and found this advice from a publisher.
Get published somewhere else. We love new authors, but some sort of track record helps a lot. If you've finished a brilliant novel and have never been published anywhere else, keep your shirt on and start sending short stories or excerpts to literary magazines; most of them accept unpublished authors, and we'll look a lot more closely at authors who have been in print before. (If you have a truly stunning non-fiction proposal, however, you might be able to bypass this step.)
Get published somewhere else. We love new authors, but some sort of track record helps a lot. If you've finished a brilliant novel and have never been published anywhere else, keep your shirt on and start sending short stories or excerpts to literary magazines; most of them accept unpublished authors, and we'll look a lot more closely at authors who have been in print before. (If you have a truly stunning non-fiction proposal, however, you might be able to bypass this step.)