Listen to whatever music which helps you work best, but be open-minded to new kinds of music which may be beneficial. Some people have a favorite sweater, a pair of slippers, or a hat. Even Mister Rogers puts on his favorite sweater and shoes before he starts working. Choose clothing which is comfortable. Loose clothing is often best, although at times more formal or constricting attire may evoke a useful sense of discipline and security.
Smells can create powerful mental associations, therefore they are useful in ritual.
Be proactive about any other needs which might distract you later. Eat, drink, wash. You may also find that physical cleansing is a good ritual. Of course their primary concern is germs, but surgeons also report that the cleansing helps them reach the proper state of mind for peak performance. When a weaver leaves a cloth half-finished, she carefully leaves a thread dangling at the point where she left off.