Do not use ultra-high temperature processed (UHT) milk. Regular pasteurized milk will work, but raw milk is best.
At the end of step 7, you may place your curds in a plastic bag and store both the curds and the whey in the refrigerator for 2 to 3 days before continuing the process.
If you want a softer-textured, moist mozzarella, do not let the curd get as firm and work less when stretching and kneading.
Speed up the cooling process in step 9 by placing mozzarella balls in an ice-water bath.