Place a whole octopus, tentacles first in a pot just large enough so that it will not move around excessively while cooking. Add enough water until it is just covered and heat until barely simmering. You do not want the water to boil or the octopus to jiggle around - lest the skin become damaged and flake off.
Cook covered for about one hour until tender. Cool the octopus in the pot until it is cold enough to lift out by its head. Lifting by the head is important so as not damage the skin on any of the legs.
The liquid that the octopus was cooked in will now be full of gelatin and flavor and will be an asset to any seafood stocks, poaching liquids, etc.