When buying raw oysters, look for tightly clamped, deep-cupped, evenly shaped shells that feel heavy and full of water. For best flavor, buy raw oysters in the fall and winter, and consume within 24 hours.
By law, oysters are sold live, in the shell. Do not buy oysters with loose or broken shells. The law also requires that the oysters are tagged with the date of harvesting. For optimum flavor, choose oysters close to your region that have been out of the water less than a week.
To examine a raw oyster before purchasing, tap on the shell. Avoid oysters that sound hollow, and instead choose those that feel heavy for their size and full of water, like a fruit. Do not buy raw oysters that emit foul odors. When an oyster is already shucked, such as at a restaurant, make sure it smells fresh before eating. For maximum freshness, buy oysters on the day of or the day before consuming. If waiting longer, East Coast oysters keep up to two weeks, while West Coast oysters keep up to one week.
To store oysters, keep them in the bag and place them in a pan, covered with a moist towel, in the refrigerator. Scrub with a stiff brush under cold running water before preparing.