Writing a book, novel, short story, or any manner of literature usually requires preparation. I like to follow a short process which includes world building, character building and more.
Step One
The first step is coming up with the story idea. This can happen at any given moment and I would recommend writing it down right after inspiration hits. With this, comes deciding what genre you want to write in. This could include fantasy, sci-fi, mystery and more. You could also do a mash up of a few genres. From here, you can write a small synopsis (book blurb), or jump right into the next step.
Step Two
This step is a very essential one. Worldbuilding is a huge part of the story you are creating. The world brings life to the characters and makes it easier for the readers (and yourself) to visualise the events taking place. To begin, start describing your world. Start off by considering the climate, resources, geography, and the languages spoken. From here, begin to outline the inhabitants of your world. This includes humans, aliens, monsters, made up creatures and more. Next, establish the history of your world. The past, the power shifts, and any major events that occur before the time your story takes place. Some questions that should be considered include-Who have been the major rulers/people with power (good and bad)? Who is the current ruler/or person with the most power? Is there going to be a hierarchical system? What events occurred during the reign of the rulers/people with power? Who are the enemies of the world you are creating? Is this a fictional world or a preexisting world? Then we have to establish the culture of your world. This includes the religion, the society, and the politics that go on in your world. The technology or power that is used in the world ie. magic, AI, and more. Two websites that outline this process in more detail and include additional thought provoking questions are listed below.
https://www.masterclass.com/articles/how-to-write-a-believable-world#4wmLufyrw7ChSuUH4wnhcG