From my own experience: 1. I have an idea in mind 2. I sort of run the plot through my head from beginning to end to see if its doable 3. Figure what kind of character(s) would work for the idea 4. I write an outline, elaborating where I can 5. Keep filling in the outline until you gradually get a piece of work you are happy with 6. go back and edit a lot.
Run blindly forward until the innumerable amount of roadblocks set you fumbling back. Then have a second go with your eyes open... It's a lot of trial and error in my experience. Buy hey, that much just reflect poor skills concerning plot development.
Think about the concept constantly. Obsess over it. Keep coming up with "What if?"s. Think about the characters involved, or, if you have none yet, put yourself in the situation you've come up with. Mull over your own reactions to the concept. Keep thinking and obsessing over it. Think about it when you're busy doing other things like chores or some such. Take down some notes if you come up with anything interesting. Keep thinking about it until it finally resolves itself into something that can be turned into a story. I find that this is how my concepts evolve--through lots and lots and lots of thinking. It can take months, depending on how big your concept is, so be ready for that.
I typically come up with a begining and a end. I create a lot of back story and outlining for longer works and the short stuff I just fly off with. If I know the character from the idea then a story just kind of follows. I typically want to know what my character's are doing and how people are reacting to them that is where my story comes from
Well, concepts aren't enough.... you'll need to develop characters and a setting, things like that. Go from there. You don't have to complicate things, so long as you have a vague idea of where you want this concept to take you, it should all grow from there.
This thread has been presented in the past in numerous variations. You have to figure this out on your own. Everyone on the forum has good ideas and opinions. Some may work for you, and others might not. Me personally? I have written 4 full novels (I'm not saying they are fantastic, but they are complete.) Now how did I do it? Well for years I kept outlines, concept ideas, book sized character descriptions and developments. I had it all neatly packed away in a filing cabinet. But I didn’t have a single written book. It took a pretty major crisis in my life, but I finally threw all 'that junk' away and sat down and started writing. The vision came to me as though I was right there, kind of like a movie. Unfortunately, once it started, it was hard to turn off. I would sit and type for days at a time, and come away exhausted. After a while I trained myself to accomplish as much as I could in four hours and then walk away, only to return the next evening. These forced breaks were tough, but gradually my concepts and ideas started getting even better. This may not work for you, but I hope you see the process I went through to discover what did work for me. Good luck on your own process.