I seem to have hit a rut. I've been working with this same idea (though it has evolved several times) for years, and every time I come back to it, I keep reviewing the same details, without adding anything new. I have the same main character, the same love interest, and the same basic plot. While the characters are now much more developed from their original, flat-surfaced selves, I still find myself with giant, gaping holes in the rest of my story that can't seem to get filled. Any suggestions? Is this some form of mutated writer's block? Things I can't seem to fill out: the villain, supporting characters, and a setting. I have vague ideas about these things, but I can't put in the tiny details.
i would suggest go do something else and come back to it. I bet you're reading the same thing over and over looking for that something you're missing or begging for some inspiration that will give you the legs to continue but it's boring you to tears. Write something else for a while, get your creative creating again and see how you are in a couple of months
start asking yourself questions, how would this happen, why did it happen, could it go worse, what does this scene need to make it better or who... the more questions you find the more answers you get think of it like a guy walking in the desert and is searching for water(sorry i live in a desert and sand is always on my mind) and spots an oasis, so how to make it more interesting? there are bandits around it or nomads, so now he has to figure a way to get to the water and not get spotted and all sort of crazy things start to happen till finally he reaches the water at the end...you get my point
It's really hard to provide any input without any details, but I agree with erebh. You can't rush it. The longer you sit around agnonizing over these points, the more it'll seem like "work" rather than something you're passionate about. Over the last few months, I've suffered the same problem. I have the central character and general ideas of the plot, but other details need filling in. To cope, I've started a few other stories and began fleshing out a completely new project (a comic script). Working on these new things has made me miss the original story, and coming back to it is fresh and I'm starting to populate some new things into it. Don't rush it!
If I were you, I'd just start writing with what you have. The right ideas tend to pop up when they're needed - actually writing focuses your attention on your story like nothing else can. If the ideas don't come, write another part of the story until they do. If the ideas STILL don't come, maybe you just don't have a story. That happened to me once. I had characters, situation, setting, all of it, but my characters just refused to do anything interesting. I didn't have a story. I gave it up and started something else, and I'm very happy I did.
I was in a similar situation. About ten years ago, I came up with an idea. I had a cast of characters, a setting, and a high concept, but no actual story. After about 5 years of work, during which time characters became more genuine characters and I weeded out the bits that were absolute nonsense, I still had a cast of characters, a setting and a high concept. I put it down for a couple of years, and worked on other things. When I came back to it, I realised I didn't actually have a story. I sat down and started working on a story, told within this world I had created. But I couldn't finish it. I knew how I wanted to start it, and I still think the start works, but the middle was weak, and I had no ending. Actually, I had an ending, one that I liked and couldn't let go of, I just couldn't GET to that ending. I haven't touched it in about 3 years. I still think about it occasionally, and there are still scenes that I think are powerful, well written etc, but I still can't think of an ending. I've reached the point where I've pretty much dropped it. I may salvage ideas from it, but I don't think the original idea I had will ever be completed. On the other hand, the project I'm working on now actually HAS a story. It also has a cast of characters, a high concept and a setting. It's working. It could be that you're the type of person I am. You're fixating on something you're attached to, even though it won't work. It might be worth just letting it go. You could also be one of those people who just needs that one thing to fix all the problems you're experiencing with what you've created. Unfortunately, finding that thing is a bitch.
Perhaps an odd suggestion, but have you considered talking about your idea to someone else? I find that trying to explain my story to my friends makes me see potential problems better. The process is something like this: I let them poke holes. A *lot* of holes. Then I ask them to help me fix them. They throw ideas at me, I shoot them down. They argue why their idea would work. I fall silent for a few minutes mulling it over and twisting it until the square idea fits into the round plot hole... They are my sounding board, my well of inspiration. I know this doesn't work for everyone, but if you're stuck, it might work to try something else. good luck! - Achira