Please don't send us something that's full of typos, misspellings, or otherwise unpolished. We won't read past the first page. We want stories that will grab and hold a reader's attention, right through to the very last page. Stories that within the first three pages make us want to know what will happen next, that introduce us to a character we can love or hate, someone whom we'll be rooting for as hero or hoping for his comeuppance as villain. We want to live the story through the senses and emotions of the characters (that old show, don't tell thing), and we want to be emotionally involved with them. Most of all we want a story that will keep us guessing right up until the last page. Of course we know that the hero will get the girl, the villain will be vanquished, the mystery will be solved, but we want to wonder HOW until the last possible moment.
Our minimum word count is 5,000 and we look askance on stories in excess of 150,000 words (do you really need that many words to tell your story?). Our best sellers are romances--historical, contemporary, futuristic, paranormal--mysteries and thrillers, and character-centric fantasies. We don't want retellings of popular titles, but original ideas and gripping plots.
If you need a label for your story, here's how we distinguish among short, medium, and long. A short story is 5,000 to somewhere around 10,000 words, a novella more than 10,000 words but less than 60,000 words (both ends are elastic). Anything over 70,000 words is a novel. Just remember, the label is not anywhere as important as the story.