Pierce the fish at the thickest point. If it flakes easily and the flesh falls from the bones, it is done. Know your product. For best results, it is helpful to know whether fish is fat or lean. Both can be used in most cooking methods, but lean fish require the addition of more fat during cooking to retain flavor and moisture.
All shellfish are lean.
Handle with care. Fish flesh is delicate, so handle as little as possible. Frozen fillets and steaks do not have to be thawed before cooking as long as additional cooking time is allotted. Do not thaw breaded frozen fish items before cooking. However, if you plan to bread or stuff fish, thaw it first.