This is the method I use to attach to BCD and also to hold regs attached to stage bottles. You can always find one of these and they hold really well.MSilvia:
Put the snorkle keeper through a D-ring, and thread one end of it through the other. This will hold the keeper in place. Put the mouthpiece of the octo through the free end, and it'll hold it securely. You'll be able to pull it out easily with a quick tug when you need it.
The bungied around the neck idea is fine as long as you and your buddies are prepared to accept a donated reg that you are breathing off. As has been mentioned above don't bungy the reg you intend to donate because it will make it hard to get off by an OOA diver. Using DIR methodology is all fine and good if everyone is on the same page but since most divers aren't the more standard methods seem to appy here.