In a wide-mouth jar, cover 1/2 cup dried mung beans or green lentils with water. It is best to use a small amount, since a larger number of beans may make it easier for mold or other types of bacteria and fungi to grow.
Cover the jar with a double layer of cheesecloth and secure with a rubber band. Let stand. After 24 hours, drain and rinse the beans through the cloth, then drain again.
Store the jar in a dark place on its side. A dark cupboard works best. Prop up the base so excess water drains onto paper towels. Rinse and drain the beans or lentils twice a day. Rinsing the beans keeps them clean and moist.
Growth usually starts within two to three days, and sprouts are usually ready to harvest after four or five days. After 36 hours, the beans or lentils will grow tails and be ready to eat, but they taste best when the tails are about 1 1/2 times as long as the beans or lentils. Rinse well, cover the jar loosely and refrigerate for up to 3 days.
