A friend of my mother's taught me this recipe. Apparently it's a standard item at izakaya.

Avoid overcooking the squid! If you do, it'll become hard and dry. Turn off the heat when you think it's cooked through! You can add ponzu sauce after turning off the heat.
If there's a lot of liquid in the pan, remove the squid, simmer down the liquid, and pour over the squid. Recipe by Haranouenoponyoponyo