Gather the ingredients. ​The Spruce Eats / Katarina Zunic

Fill your largest pot three-quarters of the way full with water. Use clean seawater if you are near the ocean or tap water with enough salt in it to make it taste like seawater. ​The Spruce Eats / Katarina Zunic

Bring it to a rolling boil and add the seaweed, if desired. ​The Spruce Eats / Katarina Zunic

Put the live lobsters (lobsters must always be alive when you buy them) one at a time into the pot. You may have to either do this in batches or have several pots going at once, depending on how many you are cooking. A standard stockpot holds two lobsters. The best way to quickly kill your lobsters is to put them in the water upside down and head first. They will be disoriented that way and will die without thrashing about. ​The Spruce Eats / Katarina Zunic

Once the lobsters are in the pot, quickly cover it and wait for the water to return to a boil. ​The Spruce Eats / Katarina Zunic

When it does return to a boil, count off 15 or 20 minutes, depending on their size. A normal 1 1/2-pound lobster takes 15 minutes to cook once the pot returns to a boil. If you are worried about them not being fully cooked, let them boil a bit longer. Undercooked lobster is not good. Overcooked lobster can get rubbery, but you have to boil the heck out of lobster to get there. ​The Spruce Eats / Katarina Zunic

Remove the cooked lobsters and place them on a plate to cool and drain. Water will drain out of them, so make sure the plate has a lip to catch it. ​The Spruce Eats / Katarina Zunic

You are now ready to pick apart your crustacean. You can either eat it on the spot or pick the meat for future meals. If you serve it on the spot, do so with clarified butter, olive oil, mayo, or a squeeze of lemon. ​The Spruce Eats / Katarina Zunic