I'm writing an urban fantasy series. Writing means piecing together whatever I've already gotten for the plot, though the current book is kicking my ass. It might also mean re-editing a completed novel.

Generally, I get an idea for a story, and if it's actually possible to expound on enough for a novel, I keep thinking about it. I develop the overall plot and usually write both story notes and snippets on my phone. When I finish one book, I start writing the next in the queue, and by that time I should have an idea of the plot, especially start and finish, the story I want to tell, the major characters, and probably have 20+ pages of snippets.

Writing those snippets is kind of odd, because not every one gets used. I've found that even if you know your plot, if you don't know the story, snippets are going to be lacking in the appropriate tone, or might just be spectacle with no substance that can be attached. Once you know the story though, it's a lot easier to slip into the characters' heads.

For research, you're going to maybe have one major topic or background you need to know of, but you'll find yourself doing a lot of inane research for little topics. You can find a lot of trivia from trying to get details correct.

As for vocabulary, it mostly matters if you expect it to be professionally published. You can use limited vocabulary, and while it might sound a bit repetitive in places, it's still going to be able to tell a story.

Regarding length, you don't have to write pages and pages if something smaller will suffice, especially for things like documentation. If you're wanting to write more about a specific thing but can't, think of other approaches to the topic. Maybe the tech can be used in a different fashion?

But most of all, the first things you write aren't going to be that good. They may even be downright terrible. You have to practice, and even then you're going to find issues with your work after you think it's ready for others. It's going to be frustrating, but it's absolutely worth the stress.