A cook’s or a chef’s knife is best for chopping or mincing; it should be very sharp. With one hand, hold the handle of the knife firmly. The thumb should rest against the blade for support, as shown.
Hold the other hand across the back of the blade and near the front of the knife. Keeping the blade tip against the cutting board, and using the tip as a pivot, lift the heel of the knife repeatedly in a rocking up-and-down motion. Gather the ingredients in a heap from time to time as you chop.