Put an inch or two of water in the bottom of a large pot with a lid. Add enough salt so the water tastes as salty as the sea - you want the lobster(s) to feel at home, don't you? Bring to a vigorous boil. If you have a steam basket or rack or pile of seaweed, set that in the bottom of the pot, if not, that's okay - the lobsters will partially boil but mainly steam and if you're cooking enough of them the bottom one or two will act as a steam rack for the rest. Add the lobsters and cover. Cook until bright red and the tail will pull away from the body, about 10 minutes for 1-lb. lobsters, 15 minutes for 1 1/2-lb. lobsters, and barely 20 minutes for 2-lb. lobsters. If you're cooking soft-shell lobsters, shave a minute or two off the cooking time.
Serve lobster hot, warm, or chilled with plenty of room to pick out the meat and make a mess. In case you're new to the game, see this How to Eat a Lobster guide for help.