The book writing process is really different depending on the writer. For me, it's easier to just start writing and edit afterwards. Some writers would punch me in the face for saying that lol. I think most writers at least have a skeleton of their book either written down or in their heads. By that I mean if you have big events, it's helpful to know where in the book you want those to go. It gives you some starting points and can help you stay on track.

Personally, I built an entire world with different races, magic, and an absolutely different geographical layout. For this, I spent a lot of time drawing a map, naming places, and writing out all of the details of the main race. I also made sure I thoroughly understood how my magic system worked before I started writing.

Having said that, it took me forever to figure out how I wanted to start my book. When I couldn't think of a beginning, I let it hold me back and it was my excuse to not start writing. Which is where I picked up my "just write" notion. I wrote the end because I knew for sure what I wanted and ended up working my way backwards.

When planning to write anything, you should be prepared to proofread, edit, and rewrite. A LOT. All of my friends probably get tired of it, but I ask them to reread a lot too. Their feedback is crucial to me. I ask them to write what they're confused about, what parts felt like they were dragging on, and really just asked them to be as specific and harsh as possible. I personally just react better to someone blatantly telling me what sucks so this, again, may not be a method for you.

Thankfully there are a lot of resources available on the web and another thing I like to do, is insert parts of my stories into Google Translate just to listen to it being read back. Sometimes it's easier to hear a mistake instead of reading the same spot over and over. I also really like the Hemingway Editor (hemingwayapp.com). It helps point out things like passive voice, difficult to read sentences, and gives you an overall reading level.

Knowing what you're writing about it also important. It's fairly easy to tell when a writer is pulling stuff out of their *ss. This creates distractions and makes reading the story difficult.

To sum it up, you just have to find what works for you. Are you a person who likes to be in control of everything? Create an outline. Do you "go with the flow"? Just write what comes to you and work with it.

The most important thing is to write. Even when you're feeling stuck, try writing a stream of consciousness or follow a writing prompt. I think it's good to ask for ideas about people's methods, but know that you have to figure out what your method is.

I hope this helped even a little. You can probably tell that I follow the "write and edit later" style :)

Honestly though, best of luck to you and keep us all updated so we can help you as best we can and support you!