Harvest the large older leaves near the bottom of the kale stem first. Break the leaves off or cut them off the stem with a pair of shears. Leave the smaller leaves near the top of the stem on the plant so they can continue growing.
Cut back the kale to the ground after it begins to flower. Flowering indicates the end of the plant's productive life, which means it's time to harvest the entire kale.
Cut the leaves from the main stem with kitchen shears, if applicable. Dispose of the main stem, which is usually too tough for culinary use.
Cut out the tougher leaf stems, or ribs, from each kale leaf if desired. Stack three or four leaves on top of each other. Cut up either side of the central rib with your shears. Dispose of the ribs. Use the rest of the leaves as desired.