I've recently begun working as a reader for a well-respected literary journal. Part of that work is recommending stories for publication, or — more likely — rejecting them. Most of the submissions I see are disqualified for a variety of reasons, and I thought it might be helpful to point out some common reasons that submissions get rejected.
1) Misspelled or misused words/bad grammar. When I'm reading critically, I'm not exactly a grammar purist, because I understand that sometimes grammatical rules must be broken in order to serve the story.
BUT. BUT. Don't tell me that a character showed "basslyness" or that a woman's hair was "perfectly quaffed." (Both real examples from two of the last pieces I rejected.) There also seems to be a current trend of not understanding when nor how to use a hyphen, which as a personal peeve drives me mad.
2) Not using spellcheck. This ought to be simple: The last thing you do before sending out your MS? Spell-check it. Over the last five mss I've read, each of them had AT LEAST one egregious spelling error that could've been caught by spellcheck.
3) Submitting too early. Two of the last five stories I've read would probably have been publishable if they'd gone through one more draft. One was a hilarious tale about two best friends who are essentially trapped in their own version of hell without knowing it. The other was a long piece about a young man hell-bent on murdering his father. Both were entertaining to read, and I enjoyed the time I spent with the characters.
That is not enough. Both of the aforementioned stories needed work to smooth out problems in syntax and story. They each needed AT LEAST one more draft/polish to be publishable. As it is, these two writers–able though they may be–aren't even getting an editorial note back. Form rejection.
Those first three reasons for rejection all boil down to one thing: carelessness on the part of the writer. Don't be careless with your work.
4) It's derivative. Cthulu may be interesting to you, but that mythology has been THOROUGHLY explored by now. If you can't offer anything new to an established mythology, all you're doing is writing (often bad) fan fic. As an example from my own writing life: I love Robert B. Parker, Donald Westlake, and Elmore Leonard. I don't have anything fresh to say in crime fiction–or at least it doesn't seem like I do right now–so I've got to explore other stories in order to be published.
Those are just a few of the things I'm seeing right now in the submission folder. Hope y'all find this helpful. I know I'm finding the actual reading to be instructive.
Edit: Thank you for Reddit Silver, kind stranger, whomever you are.