1. Start with fresh fish: Your best bet is to buy seafood from shops and vendors with high turnover that keep their fish well iced.
2. Avoid fish that was frozen and thawed in store: It's hard to know how long or at what temperature it has been left to thaw. Better to buy the fish frozen and thaw it carefully at home.
3. Keep fish fillets on ice: Take the advice of Helen Rennie, an avid blogger about fish. She suggests packing your fish fillets between layers of ice pack sheets. Refrigerators aren't normally cool enough to keep fish for more than a day, but by changing out the ice packs every day until you're ready to cook your fish will keep for at least a few days.
4. Let your shellfish breathe: Oysters, clams and mussels are best eaten within a week of harvest, but, according to Taylor Shellfish Farms, they'll stay fresh during that time if you store them in the refrigerator in an open container covered with a clean wet towel.
5. Freeze your fillets: If your plans change and you won't be able to cook your fish before it spoils, freeze it. Wrap individual fillets in plastic wrap and place them in the coldest part of the freezer, usually in the back. Be sure to label and date each pack. Small, fatty fish will keep for 3 months, leaner fish will keep for 6.
This post is part of a series: a Week of Fish. Check out our post about the documentary "Jiro Dreams of Sushi", our guide to choosing safe and sustainable fish, and list of 4 great places to shop for seafood in NYC.