Lie the lettuce on its side and cut off the stalk.
You can trim off the stiff white part at the base of the leaves if you want a more tender lettuce.
Try to keep the "heart" of lettuce, kids love to find it in their plates.
Put the lettuce leaves in a large container of water that is not too cold (more efficient at removing any earth), adding 1 tablespoon white (spirit) vinegar.
Leave the leaves to soak for 10 minutes or so to wash them.
After this, "play the spider", which means remove the leaves from the water by lifting them out with your hands. This leaves any dirt at the bottom undisturbed.
Put the leavves in a salad spinner and give them a good whirl.