Now that I want to try writing fiction again, I thought starting with smaller projects would be a good start. I vaguely remember writing a few short stories (or one shots) growing up and encountered some major challenges along the way. Due to my inexperience with story telling, I was unable to work around these. I fear about running into these again, so here are a few questions for tips: 1. How many characters should there be in a one shot? 2. How can one write solid character development with so little space? 3. What do you consider the ideal length for a short story? (my old ones were around 20 pages, but they felt rushed) 4. Does the scale of the story need to smaller in order to accommodate the short length?
I regularly write one-shots for fanfiction, so here's my thought process for them. First, I don't think there's any set rule on how many characters should be in your one-shot. Include how many or how few as you want. In general though my one-shots focus on just two characters, with maybe a few more mentioned or in the background, but not really focused on. This helps me to have the characters be able to play off of each other, but not crowd the whole thing. For the character development, It's kinda different for me because I'm writing fanfiction so the characters already have development that I can play around with, but I still usually just choose one or two things to focus on, and I don't worry about having them growing as characters too much. Most of my one-shots end not really with character development, but with thoughts that can grow into potential development. One-shots are short, and development is a long-term process, so I think it's okay to show just the little baby steps of that process. The ideal length of a story differs for everybody. My one-shots are usually longer than my individual chapters for multichapter stories, but not always. I don't really worry about length, I just write until I've reached what feels like a natural conclusion. Sometimes this looks like 2,000 words, sometimes this looks like 8,000 words. And I don't think that scale and stakes have to be small just because the story is shorter, though you may find that it happens naturally (at least, it does for me). Stories don't have to be epics to be good. Sometimes low-risk stories can impact the readers more than some high stakes stories can, it all depends on how well it's written. Write what feels most comfortable for you, and don't worry about what other people may think about it. There isn't really a set 'one way' that things should be done. I hope some of these helped.
I'm not an expert in, well, anything. Regardless, I'll try to spit some ideas at you to consider or reject as you see fit. 1) As many characters as you need. You can write a story with only one character (or even none if you want to get weird). I could imagine a story of two people locked in a medieval dungeon, talking about what got them put there and their regrets and their wishes to get out; all without mentioning other individuals directly or indirectly. Alternatively, a solo cross-country road trip meeting twenty people in 3000 pages, each of whom teaches the protag something along the way. As many or few as you need. 2) Stick to things that are important. Not necessarily important important, but everything needs to be a significant brush-stroke in the picture you're making, whether character or setting or narration, everything should have intention. One place I go to for how to do this is a thing called "The Moth", which is sort of a public event (and radio show and podcast) that gets held in cities across the world where locals go onstage to tell a true story from their own life. A few online episodes ago I heard a man spend just 10 minutes telling the story of how he swore to fight racism every day of his life, and that the men who beat him to within an inch of his life would come to wish they finished him off. 10 minutes spoken, endless awe. 3) Probably the word count Gazi said is nice. 500 words is quite short but is unlikely to scare readers away for its length, and I would be more comfortable putting something into 2000-3000. I've read published short stories that (guessing from memory and estimation of reading time) probably run 15000 or more. I probably want to circle back to the character count question. If you can write a six-word story like Hemingway, go for it. If your story runs long, then you have the freedom to make it a not-short story. 4) Scale is always weird. If the scale is too small, the reader might feel cheated. "I sat down and read this for 5/10/120 minutes for this ending?", but if you try to make it too much of a life-and-world changing event, the whole thing might topple by its own weight. I think the best thing to do for a short story would be to pick a situation where the main character would look back and say "I changed on that day". If you didn't change that day, then it's not a story, it's an anecdote. If the entire world changed that day, then it's not a story, it's an epic. Again, I'm an expert in nothing. Consider or disregard as you see fit.
Gazi and Absolute here really do have great points and you should heed their advice as much as mine. My own personal interpretation of writing is that there are no rules. Its a creative process so the moment your limiting yourself, your limiting your work. The only thing you should ever worry about is quality. How many characters should you write? The exact same number for any other story, as many as you need. How to write solid character development? The exact same way you write solid character development for regular stories, with quality, practice and examples. How long should it be? Exactly how long you need to make it. Not all stories are created equal and you will sometimes need a whole 20000 words to tell your story and others just 5. How grand do you want to make it? How ever grand you want to. This is one that I think deserves special emphasis. A short story like this has to be complete and has to end like all other stories, but you can write anything you want. You could easily make a whole short story about god creating the universe and make it a fantastic short story about him asking himself what is moral (going back to the character side to this idea, it could be just personal dialogue with god himself (1 character), or he could talk to a whole pantheon (+10) characters. It truly is only limited by the kind of story you want to tell.). The grandeur of the story is irrelevant. The story that you want to tell is the story you will tell no matter how big or small.