I usually begin by writing snippets of ideas down in a notebook like a moleskin. Love those..my son-in-law, Andrew got me hooked on them.
Then I'll write more fleshed out steps, which become the story outline, in leather-bound, old looking journals, that for the most part my kids have given to me as gifts. Don't think I've purchased any of them.
From there the outline goes into a writing software called Scrivener. I work on a Mac Mini with a Samsung 4K monitor...or an iMac. The full first draft is written, then edited several times before being sent to an actual editor.
Although the area around the keyboard and my art tablet are normally free of clutter, the rest of my desk and room are NOT!
Notes and books are everywhere and I ping pong amongst it all....sorting thoughts into a fun and surprising story.
It happens when it happens. My head is full of ideas and scenarios. They get written into the famous notebooks or directly into Scrivener at ANY time of the day or night. I've learned the hard way...NEVER leave a good idea to be written down later.
Only thing that guarantees is that it will be lost and forgotten. Darn and Blast!
I still see a few patients and run testing, so it goes without saying my days are interrupted. However, with time, I'm blocking off more dedicated time to write and do the artwork. (Just enrolled in another art/photography course, in fact.)
I do work in complete silence, unlike many authors. Music catches my attention and drags my thoughts off the page, so when I'm home alone, it's like a morgue in here.
Everything goes into here...and the software I write in is Scrivener. You can track that down at Literature & Latte. Originally developed for Mac, there is now a Windows version. I love it!
And of course, Photoshop for the artwork, with my trusty Wacom tablet. Match made in heaven...
Reference books and books for reading, fiction and non-fiction. An author needs an ongoing, ever growing stash. I can spend days in bookstores, especially older ones with books from yesteryear. Ancient knowledge is a wonderful source for a fantasy writer.
I have these all over the house, but I always start one large, new one for every book I write. Then I'll transfer jotted ideas into the main journal...from there, the actual story comes life into Scrivener.
Creativity is putting your imagination to work, and it's produced the most extraordinary results in human culture.