Nice to see someone with a passion project, can't wait to see how it will turn out. You inspired me to pick up my idea too, haha.
I can only support you to follow your idea.
Even if you don't publish it, or only make a small story, it's a very rewarding activity, depending on what you await from it.
You won't be the same person.
I'll post drawings and sketches later once I have enough.
I don't have any particular method. And I never published anything, so I don't think I'm the best one to give any advice.
Often, it begins with an idea, a character, or a dynamic between two characters, or a scene, and I build around that. Once I has enough material to give me a good idea of what the whole thing will look like, I start to write, and re-write, and re-re-write the story and the characters.
I need to write to have ideas. Others don't, it really depends on the person.
I also like to draw maps, decors, the clothes of the inhabitants. It helps me to immerse myself into the story.
Often I also need to take a break, let my mind think about it in the background, and when I work again, new ideas are ready in my head. I often work on several stories at the same time, as they feed each other. But this only works for me during the phase were I'm looking for ideas. After that, I focus on one.
But I noticed that the more you work you world and the characters, the easier it becomes to write the story, because you have more and more elements, and at one point the pieces begin to fit from their own.
I'd say, it highly depends on what you want to write.
I don't intend to invent a new genre. The structure of this story will be a classic.
If it works and get the job done, then it's good.
The less the better here.
But others might want to write a very complex story, with lots of plot twists, treason, tones of characters and secondary stories, etc.
It's neither better nor worse, just different.
One thing I learned from a writing coach who gave me an express course, as we didn't have a lot of time, is to read the dialogues aloud. Play it, like at the theater.
It forces you to find the voice, the personality, the posture of each character. And if a text is hard to say or sounds strange, then it's probably badly written. It's a good exercise to do with other people's work : if you find a dialogue fishy, try to read it aloud. It never fails. Not to criticize them, but to train yourself.
We've work on a small, but very important passage of an older story with this method. I've re-written it 6 or 7 times with this method. But the end result in a trillion times better than the first shot, and it can still be improved. It's slow at the beginning, but the more familiar you are with you characters, the faster it becomes, and at the end, it becomes a second nature and you don't need to play your text anymore. You hear the voices in your head, the characters speak on their own. But it won't make you crazy, I swear ! Hahaha. Ha-ha... Ha...
I try to always do it now with my main characters.