The secret to successful whitefish cookery is to not overcook it. Whichever of the following cooking methods you choose, your whitefish will be cooked when its flesh becomes opaque yet is still moist on the inside.
Place whitefish in a greased baking dish. Brush with melted butter or oil and season with salt and pepper, or cover with a piquant sauce. Bake in a preheated 450F (230C) oven until flesh is opaque but still moist, about 10 minutes per inch (about 2.5cm) of thickness.
Place whitefish on perforated foil on a grill about 4 inches (about 10cm) over hot coals. Baste frequently and turn once halfway through cooking period. Because whitefish is lean compared to other high-protein foods, it does not exude a lot of self-basting fat. Be sure all grills, baskets, racks, and foil are well-oiled to ensure easy handling of whitefish while barbecuing. Marinating and frequent basting will keep whitefish moist and flavorful. The fish is done when the flesh is opaque but still moist.
Place seasoned and/or marinated whitefish on well-greased broiler pan. Broil under preheated broiler 4 to 5 inches (about 10 to 12.5cm) from heat. Fish is done when flesh is opaque but still moist.
Coat whitefish fillets with seasoned flour or crumbs and fry in a small amount of hot butter or oil, turning once halfway through cooking time.
Bring poaching liquid, consisting of water, broth, and herbs and spices, to a simmer. Slip whitefish in, then cover the pan and keep liquid at a simmer for about 8 minutes per inch (about 2.5cm) of thickness.
Place whitefish on a greased, perforated rack over 1 to 2 inches (about 2.5 to 5cm) of rapidly boiling water. Cover with a tight-fitting lid and keep water at a constant boil through cooking time.