People get scared of octopus because they think it will be tough and rubbery. If you cook it properly there's no need to worry.
Heat some oil in a heavy bottomed casserole dish and throw the octopus in for about 30 seconds, then turn the heat right down and leave it simmering gently on the hob for a couple of hours (no need to add water, the octopus releases all the water it needs to cook in). It's tender when you can slide a knife in to the thickest section without resistance, just like a potato. Cook it for too much longer and it will dry out and become tough.
There are so many fabulous ways of cooking it. I stewed it with some garlic, fennel, salad onions, thyme, bay and peppercorns.... adding fresh podded peas at the last minute and garnishing with fennel fronds and a good lug of olive oil. You could stew it with tomatoes and olives, or maybe add some potatoes. The skin of the octopus dissolves and turns the coking juices into a goopy, rich stew. I chopped the tentacles up into bite sized chunks before stewing them and boiled the head in bouillon for later use in a seafood salad. Don't waste any of this beautiful animal, it's all edible.
Make sure you freeze it for a couple of days before cooking (or buy it ready frozen) as this breaks down the cell structure and makes it easier to cook and more tender to eat.
The only problem with octopus is that it looks so beautiful uncooked that I am always sad to chop it up!
Recipe and photo donated by Aaron. I have to come cook with you sometime soon!