from what i have learned writing my story is to start with the very basics. who are ur characters? what is their personality? when writing a character, especially when they are talking/reacting you need to stay consistent so your readers can automatically identify who they are. your characters are #1. getting a good backstory for them and having great character development. truly building a character that ur readers will cherish. then you need to figure out you major plot points. what are some events you want to happen? what kind of twists can you do? is this a tear jerker or perhaps an adventure? then from there you have a good foundation and a general idea of how the story will play out. its good to leave space for creative development. when i write i tend to go off rail because i thik of something new this tht. imo its a good idea to brainstorm different concepts when youre not sure how to write a certain part or when u have writers block just stat saying/writing random shit and the creativity should flow. theres no set rules on how to write these are just things that have helped me regulate the flow of my story. take breaks too!!
All of my projects have a dedicated document where I put all my ideas! No organization or rules. Sometimes its just me talking to myself being confused lol. And that's okay, cause It's really hard to organize yourself when you don't even know what you're stuck on. Ranting in your document is a good start to overcoming any roadblocks. Good luck!
What I usually like to do is this: Once I create characters and a general idea of what I want to happen in the story, I make a timeline of all the most important plot events. Usually, I do this by chapter. For example: "Chapter 1: [this character] introduces themself through [this action]." (If you need a recommendation on how to do this: I often make a Google Sheet for it).
Once I sort out how I want the story to play out, I begin writing the story itself. If you get stuck somewhere, but have a really good idea for a later part, you don't have to write it all in order. You can place the event summary from the timeline in brackets where you get stuck, and write the part you have ideas for while they're still in your head. I find this to be extremely helpful too.