With oysters, as with all shellfish, freshness equals quality. Buy the local oysters if you live in a region that has beds. Otherwise, look for the famous New England oysters. (These oysters grow slowly, taking up to twice as long to reach maturity as its cousins from warmer places. I believe that the combination of cold water and slower growth is the reason our oysters have so much character and depth of flavor.) A very fresh oyster feels heavy for its size, as it is full of liquid that tastes of the sea. Oysters that are at all dry are old and tired.
Store oysters refrigerated with the deep side of the shell down. They should be kept moist by mixing in some rockweed, and they should be pressed tightly against each other, making it hard for them to open their shells. The best container is a sack made of burlap or some other porous material. Remember that any oyster found open is dead and must be discarded.
Opening an oyster is strictly a matter of leverage. No brute strength is required or necessary. At least one hour before opening, scrub the oysters under cold running water. Place them flat on a pan in the refrigerator, with the deeper (and rounder) half of the shell down, allowing them to relax. Remember, they are living creatures; too much shaking and handling will make them tense and harder to open.
Hold the oyster, flat side up, in a cloth or towel, pressed firmly against the work surface. Do not try to open an oyster in midair as you would a clam. Place the tip of the knife in the Achilles heel and turn your hand as if you were turning the throttle of a motorcycle, pushing in with steady pressure until you feel the snap. Now give a fill twist to make enough of an opening to slide the knife along the top of the shell, cutting the muscle. The top of the shell is now off and all that is left to do is cut the bottom muscle. Keep the oyster level at all times so as not to lose any of the juice.
Always serve oysters on crushed ice, which holds the oyster level and keeps it cold. For shucked oysters simply slide the oyster and it’s juices into a small container and keep refrigerated.
Excerpt from “For the Love of Oysters,” Yankee Magazine September 1990.