You can tell if a fish is done when flakes separate easily with a fork. Bread and deep fry until fish is golden brown on outside. Pan frying can be done also. Steaming and Simmering-Can be done in foil or on a rack over boiling liquid. Wrap fish in cheesecloth or parchment paper or put on a wire basket over liquid.
Large fish do better for steaming.
Use vinegar or lemon juice in water. Serve with a sauce. Shellfish-Use moist heat. Use a lower temperature and short cooking time as shellfish are toughened by high temp. Simmering water is best.