To make fresh mozzarella cheese, coagulate milk into curds, drain whey and slice the curds, spin the curds under high heat until they are shiny and smooth, and rest the cheese at room temperature for about 20 minutes. If storing or refrigerating the mozzarella, wrap it tightly in plastic first.
Pour about a teaspoon of citric acid in a cup of water, and stir until it dissolves. Measure 1/4 cup of water in a separate bowl, add 1/4 rennet tablet and stir until dissolved. Pour a gallon of milk into a non-reactive pot, add the citric acid solution, and set the pot over medium-high heat. Stir gently until the pot warms to 90 degrees Fahrenheit. Remove the pot from the heat, add the rennet solution, stir for 30 seconds, and let the mixture sit for 5 minutes.
When the curds form, make several horizontal and vertical cuts to create a grid-like pattern. Place the pot over medium heat, and stir slowly until the curds warm to 105 degrees Fahrenheit. Remove the pot from heat, and stir for another 5 minutes. Microwave the curds for one minute, drain the whey, and fold the curds. Sprinkle some salt over the cheese, stretch and shape the curds, and use the mozzarella immediately or keep it refrigerated.