My ceremony while watching anime is usually just to eat if I'm hungry, but I always fill up a cup with water. Can't be watching while thirsty. That way you'd be focused entirely on the show. For a show that I know requires more attention, I'd eat beforehand so I don't worry about my food while watching. Subtitles can actually be intrusive to the experience, but not really for the most part, especially since dubs can take away from my immersion, so I keep the subs on.
For manga, I try not to listen to music. I feel like doing that invokes a certain bias when you're reading, unless the tone of the music is entirely neutral. A few classical songs can fit the bill, and if I do listen to music, I listen at half volume as to not distract.