Recipes:
Octopus with Lemon & Oil
Octopus with Wine & Fennel

Select your octopus for the intended purpose. If you are going to serve with the skin and sucker disks intact, 3-1/2 pounds is about as large as you want to go. Larger and you'll have to cook it so long the skin will be comming off and it'll look ugly.

If you will be rubbing off the skin and disks to get smooth white cylinders, select an octopus 3 pounds or larger, so the tentacles are still a reasonable size and you don't have to overcook to get the disks to rub off.

It is best if your octopus has been frozen which tenderizes it to some extent. Refreezing won't hurt either,

1. Octopus sold in Southern California markets is already cleaned but if yours isn't, make a cut under the back of the head where it joins the body and pull out all the innards, turning the head inside out as needed. Force the beak back from the center of the tentacle star until you can cut it out and cut out the eyes.
2. Bring plenty of water to a boil - it needs to be deep because of the way the octopus will curl up. In Italy where much octopus is cooked they put one or two wine corks in the water to help tenderize the beasts. There's no scientific explanation for this and I know of no rigerous testing, but I have the corks so I toss 'em in. In other octopus intensive areas they put in half an onion so I toss that in too.
3. Put the octopus in the boiling water and watch it curl up. Bring the water back to a boil quickly and simmer for as long as it takes. You can test doneness by inserting the point of a small skewer through the thickest part of a tentacle. When the point goes through without finding rubbery resistance at the center it's done. Here's my test results from a 2-1/2 pound octopus.

   Cook Time .	Weight .	Condition
   As bought	2-1/2 #	Raw
   Drained	2 # (80%)	Raw
   10 min	14 oz	Chewy
   20 min	13 oz	Rubbery
   45 min	13 oz	Very chewy
   1 hr	13 oz	Less chewy
   1-1/4 hr	13 oz	Just edible
   1-1/2 hr	13 oz (33%).	Tender enough, good flavor - skin still intact but delicate.
   1-3/4 hr	13 oz	Tender, flavor still OK - skin wipes off, suckers with more difficulty
   2 hr	9 oz (23%)	Tender, flavor starting to decline - skin and suckers rub off easily

4. If you cook to the "Tender enough" point, leaving the skin and sucker disks on (my recommendation), the skin will become firmer and adhere better when the tentacles have cooled. Octopus gets a bit stiff and has less flavor when chilled so you always want to bring it to room temperature for serving.