A few months ago, my friend Henry (who dabbled in short fiction) and I (a fan of writing longer work) had a debate about the merits of short stories vs. novels. "I feel like if a short story doesn't have a satisfying ending, I at least won't have to read two hundred pages and then get disappointed," said Henry. I argued that most novels, within the first few pages, set up the reader's expectations accurately, and that I put down novels I dislike within the first five pages, anyway. The problem with a short story, in fact, was that in many cases, I couldn't invest myself enough in the characters.
Then he brought up a point: "Y'know...what bothers me about novels is that the protagonist needs to change in order for it to be complete. [With the exception of Holden in The Catcher In The Rye.] It's different with short stories--as a character, you can stay the same and it'd still be a good story. Maybe our preferences have to deal more with how we view life, though. I don't like having to change."
It was an entirely accurate observation, albeit too deep for our surroundings at the time (newspaper class, and all around us anarchy reigned). But my point is, neither form of prose is better than the other; you just expend different types of effort. When novelling, word count was the last thing on my mind--in fact, the more words I had, the better, because my plots are simplistic. When I work on short stories, though, I always find myself trying to simplify the plot even more for the sake of economic word usage. There's also the issue I had during novelling, of whether the reader would care about my characters...except multiplied about fifty times in importance.
Anyway, here's how to become adept at writing short stories (though honestly, this technique applies to everything else, too).
First off, write a short story. Do not use any outside resources: do not read any writing books, do not peruse writing websites online, do not read short stories. Everything should come purely from you. Write a story you've been meaning to write, but never got around to because of silly reasons. Save it in a new flash drive folder entitled SHORT STORIES. Name it Before.
Now! You are free to use outside resources. In fact, exhaust them. Check out old issues of The New Yorker from the library and while you're at it, fill up your basket with collections like "The Best American Short Stories" and magazines like "Writer's Digest." Refrain, if possible, from perusing the Internet for research. The Internet is filled with dubious sources, and you'll find that most stellar writing exists in print form, anyway. Here's an exception, though: The Sun Magazine, which is free to access online. Read, read, read. Absorb.
Photocopy/scan truly remarkable pieces and amass them in a folder, whether it be physical or electronic. Find more stories from the writers you like and read those, too. This research should take 25-50 hours total. If you don't feel ready to move on after 50 hours, you're probably wrong. You'll be ready.
Start a 30-day project: formulate 30 premises of short stories you've wanted to write. Type it up in a Word doc and save it in your SHORT STORIES folder. Print multiple copies of this list out. If you can't think of 30, that's okay for now. Go back to the list in another week. If you really can't think of 30, here is a great Tumblr of writing prompts. Premises can be anything from one sentence to a detailed outline of each story (I find outlines constraining, though).
At this point, you should write a story a day from your 30 premises and save them by day number in the SHORT STORIES folder. Each day, write in the voice of a different writer you like. This is very important even if you've found your voice; I take risks with short stories that I normally wouldn't in novelling. What about time? you ask. Write when you're waiting in line. Write on bus rides. Write on scraps of paper or (thank you, technology) in whatever Notes app your phone came with. If you don't think you can handle a few thousand words per day, then don't! Limit your stories to flash fiction length if need be. The only rule is to get it done. Finish it by the end of the day. Do not use any other day in the 30 day project to go back and revise. Even if you have free time.
Once you've finished story #30, write from the same premise as you wrote Before, without looking at the actual piece. Name it After. Compare Before and After.
You can now revise your 30 stories (!).