The markets I'm trying the hardest for right now are BCS and Clarkesworld. I read stories from them frequently, but I guess I just haven't read enough yet?
What happens after you read those stories is what matters. There's an old saying in publishing that editors "want something just like everything else. . .only different".
There's a lot of truth in this. Too many read many issues of a magazine, and then give the editor a story just like all the others he's published. This sometimes works, if the story is truly exceptional, and extremely well-written, but it doesn't work often. The reason to read all those stories is to give an editor a story that's constructed the way he likes, that's the length he likes, and that has the pace he likes, but that contains something no other writer has given him, or can give him. This is the all-important "only different" part of selling stories.
It's tough to explain, but there's only one thing you can give an editor that no other writer in the world can give him, and that's yourself. It's your life experience, it's your take on people, it's your take on the human condition, and it's your sense of both the dramatic and the humorous.
Many who try writing, and even many pro writers poo-poo "write what you know", but I've found that even writers who poo-poo it still do it. Read Ann Rice, and New Orleans, Catholicism, and voodoo all come alive, even though she's one of those who doesn't believe in write what you know. The same is true of Stephen King, and pretty much every other big name writer I've read.
Write what you know doesn't mean you can't write about life on other worlds, or vampires, or witches, or werewolves, or serial killers, or anything else. It means that whatever you write about, you have to understand that you're still writing about people, and about the human condition. It means you're still writing about your life experience, the lessons you've learned, the places you've been, particularly the place you grew up, and all the people you've known. It means you're writing about your take on what it all means, on what's important, on what's right and what's wrong, and on how people behave in any situation.
Ray Bradbury moved his hometown to Mars. Doing so made him famous. Place matters, setting matters, and done well enough, both sell stories. But people read for the characters. Long after plot is forgotten, good characters remain in the mind. If you give an editor a place readers want to visit, a setting that's detailed and realistic, and characters unlike the people they know, but who still ring true, selling stories gets pretty easy. But the way you do this is by getting YOURSELF into the stories.
It sounds easy, and it is, once you learn what it really means. Read those issues, and ask yourself what the editor hasn't published. I don't mean plot. In all of this, plot is the least important. If you can't come up with a decent plot, all is hopeless. What setting has the editor never used? He's certainly used big cities? But is there a city you know so well you can make it seem like something he's never used? Probably not. But if you grew up in a big city, I'd be willing to be the editor has never had a story that used your neighborhood, the small, one or two block area that you know well enough to describe every crack in the sidewalk, every stained brick, every dirty alley, and as important, the unique people and businesses located there. Bring that setting alive, pull those people out of your memory and put them on paper. Even if you then move this block to Mars, or to some distant galaxy, it will, if you write it well enough, sell that story.
Dramatic things happened there, too. Even if you didn't witness them, I'd be willing to bet you heard about them. Humorous things, as well. Some managed to leave that neighborhood. Others had to stay. Some had lousy home lives, and some had great home lives. Some were good, some were bad, some were happy, and a couple were mentally ill.
What happened to you there? What were your thoughts, your hopes, your dreams? Same for the people you knew there. Who were they? What did they look like? What jobs did they have? Which one would make a great engineer on a Starship? Which one would kill anyone who even looked at his wife, and how would he kill them?
How did it feel to walk down the street there? What did it sound like? What did it smell like?
It's your experience that sells stories, even if you show those experiences through a werewolf or a Leprechaun. It's setting. It's detailed, make the reader know it's real setting, even if you move that setting elsewhere. More than anything, it's characters the editor has never seen. They don't dress like all the other characters, they don't have the same professions as the other characters, but they're so real the editor catches himself asking them questions.
You have to be able to write reasonably well, you have to be able to tell an actual story, but it's getting yourself into those stories that separates you from all the other writers who submit stories.
Never let anyone tell you good, detailed, realistic description doesn't matter. There's a phrase used to describe people who don't understand the importance of description in both setting and character. They're called "unpublished writers".