You’ve written a short story. Since you’re on the SF Story of the Day website, I will assume for the purposes of this post that your story can be described as speculative fiction (whether it be science fiction, fantasy, horror, slipstream, or any other subgenre that fits under the speculative umbrella). You want to get your story published, and you’re not sure where to start looking for publishers who accept unsolicited submissions of speculative short stories.
The first place I always look for opportunities to submit my work is the Science Fiction & Fantasy Writers Association’s monthly market reports. These are publicly posted on the SFWA website, which means you don’t have to be an SFWA member to read them. The reports are compiled by David Steffen, who also edits the excellent SF magazine Diabolical Plots and runs The Submission Grinder (more on the Grinder in a moment).
As an aside, one important thing to keep in mind while you are browsing market listings and submission guidelines is: What is the word count of your story? If it is 6,000 words, you want to look for publishers who will accept stories that long. Beneath Ceaseless Skies does. Flash Fiction Online does not. So, it makes sense to send that story to BCS (if it fits their other guidelines). It does not make sense to send it to FFO, as they cannot and will not accept it, no matter how fantastic a story it may be; a magazine that only publishes flash fiction (a category with varying definitions, but that rarely includes stories over 1,500 words) is simply not going to accept a full-length short story. Even if the editors love that story, they don’t have the budget to pay you for it or the space to print it, so it’s best not to take up their time (or yours) with a submission that does not match the magazine’s scope.
The above holds equally true for other details you will find in each publisher’s submission guidelines. If a magazine says they do not publish stories containing animal death, and your story contains animal death, it is not a good fit for that magazine (even if it is a really great story). You will be much better off submitting it to a magazine that does not specify “no animal death, please” in their guidelines! If a magazine says “we are only accepting submissions from writers of [insert specific background or identity here] for this submission call,” and you are not a writer of that specific background or identity, submit somewhere else this time around and wait for that magazine to open up a call that applies to you—or simply make a list of other magazines whose general guidelines are applicable to your situation. If a magazine says “we can only accept submissions from Canadian writers,” and you live in Wales and do not have a Canadian passport, it will not serve you to submit to that magazine, as they will not be able to accept your work. Always pay attention to the guidelines! It can take months and months to hear back from a magazine regarding your submission, and it will probably not be a rewarding use of your time to wait that long only to find out that your story was rejected because the publisher was looking for novellas and you sent them a drabble. Save the drabbles for venues—such as Martian—which are actively seeking work in that category.
Now, about that Submission Grinder I mentioned a few paragraphs ago. The Grinder is an invaluable tool for writers in many genres and forms, but it is particularly well suited to the needs of people publishing in the SF magazine and anthology world. The Grinder maintains an extensive database of listings for publishers and publications, and has excellent search functions that allow writers to do things like narrow the listings down to, for example, publishers seeking short stories of 3,500 words in the genre of horror. If you make an account, the Grinder also serves as a tool for tracking your own story submissions—and uses the tracking data to provide information on the publisher listing pages such as the average time it takes for that publisher to respond. The Grinder isn’t the only website which allows writers to both search for publishing opportunities and track their submissions—Chillsubs is another such tool—but it is free and easy to use, and a wonderful part of the online speculative fiction community.
There are plenty of other places you can look to find listings of submission opportunities. For writers whose work leans dark, The Horror Tree often features interesting listings. For writers who dream about being published by a specific magazine or anthology-focused small press, following that magazine, press, or group of editors on social media or signing up for the relevant mailing list can be a good way to keep track of when your dream publisher is taking submissions. For writers who have already published an SF story or so and qualify for membership, the Codex Writers’ Group forum can be a great way to learn more about magazines and publishers to which you’re interested in submitting your stories (Codex is a great resource in general for those of us who are just getting started in speculative publishing, and a great way to maintain a sense of community among SF writers).
Now that you have a list of places to look for publishers that might accept your short SF, the best tip I can offer you is probably one you’ve already heard, but it is important enough to bear repeating: Read the magazines and anthologies you think you want to have your stories published in! Get a sense of what kinds of stories, what types of themes, what styles of prose, their editors are into. Get a feel for their general vibe. If you really love a magazine, sign up for their mailing list so you’ll be the first to know about their upcoming submission calls. Really get to know the markets that make sense as venues for your work. Nothing guarantees that a story you submit will be accepted–most magazines receive hundreds, if not thousands, of submissions, and have to reject nearly all of those submissions–but understanding your markets will heighten your chances of finding homes for your stories.