Cut the fins off with scissors. At the base of the tail end, take a sharp knife and scrape up a little of the skin. With a kitchen towel in one hand and holding the fish down with the other hand, peel off the skin. It should come off in one piece with a little effort.
To prepare for grilling, slice through the middle of the fish from head to tail, then cut away from the bone to open up the fish, as if you were cutting away a fillet, but not all the way, creating a 'collar'. Do the same on the other side. Snip the bone at the head and tail with scissors and when the fish is cooked, you will be able to easily lift away the bone.