Here are a few quick tips about buying fish according to whether you're buying Fresh Whole Fish, Fresh Fish Steaks or Fillets or Frozen Fish.
Fresh Whole Fish (below) should be nearly odor-free and have bright, shiny scales that are not coated with a slimy film.
Fresh Fish Steaks or Fillets (below) should look wet and shiny, not slimy and dull, with flesh that is translucent and bright, not bruised or opaque. Fresh fish flesh should also look elastic, not mealy and should have almost no odor to it. If the fish is wrapped in plastic, check the “buy before” or “sell by” date on the price label. If the date has passed, make another selection. For further questions about fish freshness, ask the person at the fish counter or store meat manager.
Frozen fish will be opaque due to its frozen state (but will become translucent when thawed) and should be bought
frozen solid, not partially thawed unless you’re using it that day.