I tend to write on weekends or very late at night. I used to only write in a notebook and then type/edit everything into my computer about once a week, but now I write on my tablet. I love the portability of the tablet and the fact that it doesn't add the little spell and grammar check squiggles while I'm trying to get the story down.
I can write pretty much anywhere, but I prefer it to be somewhat quiet and mildly lit. Usually, at home. I also write during my son's Taekwondo practice, unless he's learning something new and I want to watch. That's a bit tough though because of all the shouting.
As for rituals, I don't really have any that I do while writing. But, for plotting that's a different story. I do most of my plotting on my drive to work or on my way home. I'll test out scenarios, dialog and plot twists aloud. I cannot have music running while I'm doing this in the car or when I'm actually writing. I also usually forget to stop to eat until my stomach complains at me, so the activity is pretty all-consuming.