My first serious writing experiences were on MUSHes. (Multi-User Shared Hallucination). MUSHes are text-based games in which you create a character, and interact with other created characters, all via text. The better you write, the more real your character becomes. You learn how to give away what you want to share about your character without coming right out and saying it. And you write a LOT. Paragraphs and paragraphs, pages and pages. You learn to start thinking in entire small blocks of action/reaction. I'd recommend them for writers as practice, if it wasn't for the fact they're terribly addictive and time-sucking.
The catch is that MUSHes are usually thematic. The point of the game is known to everyone, and the plot is known ahead of time. Rather than moving from a beginning to an end, your characters are moving through time, moment by moment, scene by scene with the endpoints in far distant future and past, unknowing of your own fate.
The downside here is that you start thinking of plots in these huge overarching waves, and your characters tend to live so much in the moment that they never go anywhere.
The one thing I learned on MUSHes though, was that characters evolve, sometimes in ways you didn't expect them to go. They'll develop phobias, or feelings that you don't agree with, or suddenly hook a left turn into crazy town without signalling.
I figured that was just an aspect of MUSHing. That in a carefully constructed plot, plan and story, that they wouldn't go rogue, because they would be taped the hell down.
I started writing about a communist gangster, because the idea amused the hell out of me. I imagined this short story that would be a humorous diatribe about how a mafioso decided to become a communist because he hated banks, and because he viewed the mafia ownership of unions as supporting the proletariat. I'd be sticking it to the man.
I initially put him in a bar with a beautiful woman, to chat about the purpose of communism and his roles in the mafia. A great contrast of two things that shouldn't go together.
So I started writing. But then out of nowhere, a plot whapped me upside the head. My characters were suddenly driving the story, and I didn't know how it was going to end. I got hijacked by my own writing.
I ended up with a 4,500 word story that I then had to go back and clean up, because the communism had become completely irrelevant to what the characters and story were really about.
I don't know what to do with it now. It was intended to be a journal exercise only. But it's got a life of its own, and I'm a little afraid it won't be content to hide in a drawer.