The preferred method of cooking lobsters.

Steaming is my preferred method of choice as it is gentler, yielding a slightly tender flavorful meat and it is more forgiving on timing.  It's harder to overcook a steamed lobster. A 4-5 gallon pot will handle 4-6 lobsters.  Put 2" of salted water in the pot, then a steaming rack and bring to a boil.  Add lobsters one at a time and cover.  Start timing 18 - 21 minutes depending on the doneness preferred.  Timing is for ALL the 1-1/2 lb lobsters in the pot. When cooking five or more, stir lobsters halfway through and cover.

For boiling lobsters, fill the pot with water, bring to a boil and add lobsters and start timing immediately.  Do not cover.  Boil lobsters 20 - 23 minutes.