Remove any discolored leaves and the small leaves at base of artichokes. Trim stems even with base of artichokes. Cutting straight across, slice 1 inch off tops of artichokes and discard tops. Cut off points of remaining leaves with scissors. Rinse artichokes with cold water. To prevent discoloration, plunge entire artichoke into 4 cups cold water mixed with 1 tablespoon lemon juice.