i think we need to have the best equipment and supplies available to us (depending on where you live sometimes) and also the best food and environment items available. my old octo tank had tons of rock with lots of hiding places, but the rock was almost all dead, with no life. so when he was moved to a better, smaller tank (55 to a 30, he is much more comfortable and less stressed) in a darker room, we bought like 20lbs of live rock for him with lots of hiding places and kept his old favorites as well.
i also believe we should strive for the most knowledge possible on general octopi and their care and also more specific things pertaining to IDing them and then reading up on that species. Another good thing is being on forums like tonmo and getting to know your lfs owners. My lfs is a bit above average in general, but they are very well versed in the care of octopi and are very picky on those thinking to order one. in fact, they only get octopi in for those specific people and pick out the octopus out themselves in person at the supplier. When i was getting Othello, they went to the supplier down in miami and picked the best one and kept him in a dark place in the back of the store and i had to pick him up as soon as they returned with him.he never even went in one of their aquariums and went straight from supplier to bag to my tank.
Much attention should be payed to the species owned and their individual personalities. I still dont know what Othello is, but i pay much attention to his actions and quirks. i know what foods he likes and what he will ignore, as well as which hiding places he likes best and what conditions he likes best. I also pay close attention to his color changes and movements and inkings. When i get him out and handle him more often, he inks less often and in smaller amounts and will actively explore my hand and arm. but if im gone for a while, like the two weeks i was gone, he has a freak out and squishes into a corner.
Making sure they are entertained is important too. Othello completly ignores anything i put in, but i made sure before i just decided he wasnt interested.
personally i think an octopus can greatly benefit from living in captivity. of course, thats only if they are cared for very well and the person in charge does everything possible to give them the best life.
the more advancements in aquarium tech and research on cephs we gain, the better their care will become.