My rituals aren't nearly as involved as some listed here, but here's mine:
While I OCCASIONALLY like to write in public (when I was in high school, I'd long for that lunch hour where I'd skip the food and write the whole time), my current WIP (a 5-novel series) has too much 'hard-paper' to take it with me to a public place. After I weeded through almost 8 years of work this past summer, eliminating papers that aren't really important to the current story (because they contained information on old plots or characters), I ended up with 4, 3" binders and 1, 1" binder - all of them full of papers dealing with the plot. I can't really take that out with me, ya know. So, I've learned to love writing at home.
While writing at home, I have to be comfortable; this means no jeans, tight shirts, and socks that aren't big roomy ones with the prickly things on the bottom. I love wearing a big t-shirt, and thick - but soft - draw-string pants. People who come over have learned not to look at me with disgust, when I head up the stairs with my hair and clothes in disarray.
I also have to write at the right time of the day. Being a writer, I tend to go all off schedule, all the time, sometimes sleeping during the day and being up all night and sometimes the other way around. Writing in the middle of the night works best for me, because everyone in the house is asleep (no distractions), everyone in the country is asleep (no annoying phone calls that disrupt my train of thought), the roads outside are quiet, and there's not a d*mn thing on tv worth watching that will distract me from my work. And for some reason, I write some of my best stuff - those rare passages that writers actually read later and still love - on the verge of sleep.
My writing environment has to be perfect, too. The first thing is the temperature: I tell ya, it's a b*tch trying to be comfortable in the hot Virginia weather, because any fan I blow towards me ends up blowing my many papers everywhere (I don't have an air-conditioner!). Luckily, autumn weather is approaching and the heat is dying down, so I don't really have to worry about the temperature of the room anymore.
I'm also particular about the lighting in the room. My 15 year-old brother hates how bright my work area is, but writers do need light and lots of it. My eyes are bad enough having discovered the very addictive internet a few years ago. Any straining to see, due to bad lighting, is sure to ruin my already flawed eyesight by the time I'm 30.
Finding the right work area is tough for me, too. I really like writing by hand and having a hard copy of everything I write. I just don't trust computers anymore. This is the second one I've had (I lost my first one to lack of internet common sense and enough spyware to take down the White House computers). And, writing everything out by hand requires a nice, again COMFORTABLE, work surface. I've tried writing at my desk but it doesn't work for me. I've tried one of those lap-desks, with the bean-bag attached to the bottom. That didn't work. I've tried one of those tiltable hospital-style, bed-side tables. That didn't work (mainly because the only one I could find less than 100 bucks was made of material flimsier than cardboard boxes). Finally I found something that did: the Table-Mate II, this white table with a work surface that can tilt to 3 different angles, and has L shaped legs, letting it fit under the edge of any couch or bed, so you can pull it right up to you - I prefer working on the edge of my bed with it. The desk is perfect for me and it was only 30 bucks.
Now, materials... The most important thing of all (for me anyway). I have to have the right materials. And for me, they are white legal pads - NEVER yellow - even if 'yellow' is 'thought to be a color which stimulated the intellect' because they, really do a number on your eyes after 4 or 5 hours staring at them - and the perfect pen: a black 'Uniball VISION Fine Rollerball Pen.' These are my favorite pens and I LITERALLY have a box with 200 of them in my desk right now. I can't use another pen; I feel like I'm cheatin' on the Uniball VISION Fine. And pencils are out of the question. I HATE pencils. I have a piece of writing I wrote in pencil about 7 and a half years ago (when I first started developing my novel series), that you can't even read anymore because the lead has worn away. You have no idea how frustrating it is, wondering what was written on that piece of paper and if knowing what it was now, would make the current story any better.
Well, I think that about sums it up. Hmm, I guess that comment above about my rituals not being as "involved" as everyone else's, was sarcasm...