The best writing advice I ever got was "Keep moving forward, don't retreat into rewrites." The worst came from a book that said "Writing fiction is like telling lies," which just seems stupid to me.
Wrote my first "novel" when I was six. Studied a bit in college, but then pursued history... But when I started writing professionally, it was mostly learn as you go.
I love magic and playing with magic systems. But to me, good fantasy like all fiction comes down to good character and plotting.
Before writing, I start with a series of questions, specific things I need to know before I can write the book... That list grows and changes as I do more and more research. But when I've answered the bulk of the questions, I begin to write...
As I write, invariably I encounter more questions and answer those as I go.
With a historical setting, I worry about accuracy at every turn... With a created world, I have to worry about all of it holding together and seeming coherent... Each presents unique challenges and opportunities.
The closer you can get to your setting and to primary sources, the more authentic your history is going to be...
I listen to instrumental jazz and bluegrass, but aside from my AM workout, I have no rituals.
I write every day for most of the work day, and I try to write 2,500 words per day... If I don't make it a routine and treat it like a job, I'd never get anything done.
Writing about craft has forced me to think more about my own writing technique, and to break down my process in ways that have been enormously helpful to me.