When I first started writing toward publication, I would come home from the day job and find it hard to transition from the stresses of the work day into the world my characters inhabited. Quite by accident I found that if I put on classical music, it was easier to get the words flowing.
I still write with music playing most of the time. On the days I don't, I find that I'm less productive usually averaging only three pages of new material in an hour and half. If I write with music on, I usually write five pages in the same amount of time, but have written up to eight pages in two hours if the words are really flowing.
I have friends who have similar ways of transitioning into the world of their characters. Some light a candle before starting to work on their manuscripts. Some listen to music like I do. I have one friend who does a few yoga poses before sitting down and getting to work.
While we all have our rituals, I never really thought about it until I came across the following:
"It is every bit like entering a dream, and just like I cannot fall dead
asleep the very instant my head touches the pillow at night, so too I
cannot flip a switch and be ready to write the moment I sit at my desk. I
must allow myself time to move from the bouncy, outward-looking mindset
of my day-to-day life to the quiet, inward-looking mindset of my
writing life. Many writers develop rituals to help with this shift. I
write first thing in the morning, immediately after meditating, feeding
the cats, and making coffee. I think it helps. We’re all a little bit
like Pavlov’s dogs in our habits." ~ William Kenower
If you're interested in reading the entire article I've quoted part of above, here is the link: Preparing Your Mind For Writing: How To Make The Shift