Clean, wash, and then dry the fish on paper towels. If fillets are large, cut them into uniform tapering strips.
Heat oil to 390 degrees. Dip fish into coating. If using one of the simple coatings, lay the coated fish in the bottom of the fryer basket and lower into the hot fat. If using the batter coating, drop fish as it is dipped directly into the hot fat. Remove each piece as it is done. Do not crowd the pan.
When they are done, drain on paper towels and keep warm in a hot oven. Serve with lemon halves, Tartare sauce, or one of the butter sauces.