Scale, gut and gill the fish. Score the fish and rub the skin with olive oil, salt and pepper. Place fish on the grill and cook over natural charcoal for about 12 to 15 minutes, flipping it midway through. The skin should be crispy before you take the fish off the grill. You may use foil to prevent the fish from falling apart, but the skin won’t end up as crispy. Serve with a couple slices of lemon, onion and tomato.