Pull off the outer leaves for harvest. The inner leaves continue growing. The whole plant may then be harvested in a week or two.
Dig butterhead lettuce up from the ground with a trowel. This saves you time later when cleaning up your garden. If you harvest every other plant, the remaining lettuce plants growing in a tight grow a bit bigger.
Cut butterhead lettuce plants to the ground with a sharp knife. If you harvest every other plant, the other plants have more space to grow.