To tell if a whole fish is cooked, insert a metal or wooden skewer into the backbone of the fish. If it slides in easily, it is done. If cooking a fillet, the flesh should be opaque in colour at the thickest portion of the fillet. You should allow at least 10 minutes of cooking time per inch of flesh thickness, no matter what type of fish you are cooking, regardless of the method.

If you are planning to cook fillets, be sure to use a roundfish, such as a cod or salmon, or a flatfish. These types of fish are not too boney. Pieces should be at least one-inch thick.

Frying and Sauteing
These two methods are excellent for cooking small fish, such as herring and small trout. Using a cast iron frying pan results in very even temperatures. Dip the fish in beaten egg, then coat with seasoned flour, or a mixture of breadcrumbs and seasonings. To saute, heat equal amounts of oil and butter in a frying pan over medium heat. Brown the fish on one side, and then the other. To deep fry, heat oil to 375 degrees Farenheit and follow normal deep frying instructions.

Barbecuing and Broiling
These two methods are suitable for almost any fish, except for very small fish such as smelt or herring. A fish-shaped metal basket is a handy tool for the barbecue.

Preheat your broiler (or have coals on the BBQ red hot). After seasoning, cook the fish 4 to 6 inches from the broiler or coals and baste often with oil.

Baking
If using a whole fish, such as a salmon or large trout, baking is probably the best method. Use a well-buttered dish and brush the fish with butter or olive oil. In place of oil, you can also top the fish with a mixture of herbs, seasonings, and bread crumbs, or even chopped vegetables. Bake fish in a preheated hot oven (400F to 450F) according to the directions in your recipe.

Another method of baking, which makes clean up a snap, is to wrap the fish loosely in tin foil that has been oiled or sprayed with a non-stick cooking oil spray. Add a sauce, seasonings, or garlic butter, and bake in a hot oven. It is important to ensure that the fish is only loosely covered to allow the steam to circulate freely, resulting in a more tender fish.

Poaching
Poaching gives you the opportunity to really test your gourmet genius! Poaching simply means "to simmer in liquid" and is best suited to firm fish, such as red snapper, trout, or salmon. To poach a whole fish, keep the fins intact and ensure the fish is well supported on a rack in the pan. For smaller whole fish, enclose the fish in cheesecloth for easy removal from the pan, and ensure the fish does not break when removing it. Cover the fish with warm liquid of your choice. Bring it to a simmer, and then start timing according to the weight of the fish and to your recipe. The liquid in which the fish was poached can be saved and used in dishes requiring fish bouillon.