Construe the word “ritual” in the broadest possible sense. It can be that you work best in a certain environment; that you need music playing, or utter silence; that you have to play 2 games of Spider Solitaire before you get down to it; that you have to vigorously couple with Debra Messing.
Also, give us an idea of what sort of work you do.
Answering my own question:
For my corporate trainer/drone job, I have to begin the day by arranging the desk. This may seem remarkably stupid, as I end the day by cleaning the desk, but I mean I gather any documents I’m going to need throughout the day, arrange them in Monklike piles, return the phone, computer, and so forth to their proper positions (the cleaning crew tends to move them ENTIRE MILLIMETERS while dusting, the bastards, even though there’s never any dust left when I leave) and so forth.
For creative writing: I must gather all reference materials I will need close at hand. My Roget’s must be on my right. My Concise Oxfordmust be on my left. Any other books go directly in front of the laptop. There must be a hot beverage at my right, and any pages to be marked up go on the left, as my array of magical colored pens without which I cannot think of abstruse allusions. I must do 10 minutes of freewriting before beginning, and I need music to listen to. This music must be something I already know very well, so as not to be distracted by new discoveries.
Reading the above makes me fear for my sanity.
For tutoring: I must assemble all materials to be used in the session close at hand. I must also make sure there are no knives or guns in reach, in the event one of my students pisses me off.
Anybody else? Anyone? Bueller?