Don't have routine but process I got... mostly.
So, I'm kind of "lightning" designer. Either the whole game comes to me all at once or... nothing. I got games that are just a title and idea and have been that way for years.
One thing I tend to do is steep myself in source material. I didn't feel right working on Necropolis for The Sprawl having only read Neuromancer. So I re-read Neuromancer, Count Zero, Mona Lisa Overdrive and the four Sprawl relevant short stories in Burning Chrome.
I'm glad I did because that lead directly to the creation of the The Sourcerer playbook because for all his lofty academic credentials +Hamish Cameron is apparently a literary monster who can't recognize that the thematic glue that holds those books together is the spiritual role of the A.I.s and completely left it out of his game! So, I was happy to fix that for him.
See what I did there? That's my process. I look for the emotional heart across multiple source works and design around that. It's why I often go to older books. Older literature is less concerned with structure and less concerned with genre tropes. I find it a much more suitable source for inspiration because RPGs are a chaotic medium built in the moment.