Well, it needs a steady supply of live food for one thing. If you can't get that, don't even try. You also need to TOTALLY close off the top of the tank. Here is a story I heard:
A guy who had an octopus didn't close off the tank. Well, across the room, he kept his bowl of feeder goldfish. The Octopus climbed out, crawled across the room, got in the tank with the goldfish, ate them, then WENT BACK TO THE MAIN TANK.
The good news is that they are not stupid. However, you need lots of places for it to hide, and toys. Yes, you need toys. I told you, they aren't stupid. A floating Hydrometer will do. What he'll do is pull it down to the bottom and let it go back up to the top. He definately needs timed lights, but most people have those anyway. Hope this helps you.