I have a very simple way of cooking squid, it does require some preparation time, but I find that the end result is tender tasty squid.
I take squid tubes and split them into a flat piece of squid, then I score the squid in a checked pattern on the inside of the squid. The key here is to cut into the squid, but not all the way through. With thicker pieces of squid this is easier than when the squid is quite thin. The technique I do, is let the knife do the work and not to press down with the knife. You really do need a sharp knife for this.
In a hot pan I add some olive oil and then quick flash fry the squid. What should happen is the squid should cook and roll.
This can then be seasoned and served, though I also use this method when adding squid to my paella dishes.