Live oysters are best as fresh as possible and therefore should be purchased from a store with good turnover. Reject those that do not have tightly closed shells or that don't snap shut when tapped. Fresh, shucked oysters are also available and should be plump, uniform in size, have good color, smell fresh and be packaged in clear, not cloudy oyster liquor. The sooner they're used the better they'll taste. Refrigerate shucked oysters in their liquor and use within 2 days.
Oysters are also available canned in water or their own liquor, frozen and smoked.
Oysters in the shell can be served raw, baked, steamed, grilled or in specialty dishes such as oysters rockefeller. Oysters are high in calcium, niacin and iron, as well as a good source of protein.