Bivalves--especially oysters-- can be tricky to navigate. Locating the best spot to insert the shucking knife into the oyster's curved hinge is the key to getting started. Show (rather than tell) a first time shucker; when approached slowly and with caution, sometimes a first attempt yields success.
The tool of choice is an oyster shucking knife. There are various types. The sides of the shucking knife are never sharp but the tip should be. The wood handled is wide and round at the end, so that it can stabilize in the palm of your hand as you apply some pressure to the oyster shell. Another variety of shucking knives is stainless steel and the blade and tip is wider. The wider tip is to grip more shell space when the proper hinge is located. Creating more of a rocking motion to open the shell, as opposed to the sharp, pop! that is heard when the shell releases from the thinner tip. The wide edged variation relies more on working the tip, so the handle is straight and does not rely on the palm of the hand as much, to create the rocking motion.
First, rinse the oysters and remove any excess shell or marine debris. Keep a towel in one hand, to hold the oyster flat on a stable, hard surface. Using your preferred hand to hold the shucking knife, find the hinge on the flat side of the shell. You should be looking at the narrow, tip end of the oyster, not at its rounded edge.
Insert the tip of the knife into the hinge and find a spot where the top and bottom shells are connected; this will give the knife tip leverage. With more wrist work then arm strength, begin to wiggle the tip back and forth, looking for the shell to separate. Continue to apply pressure with your palm, gently rotating your wrist until you can carefully pop the shell open. The knife should remain in the shell, flat and pressed upward, to separate the oyster from the shell without tearing it. After removing the top shell, tuck the knife under the oyster to loosen it from the foot (the muscle tissue on the curved side of the shell that connects the oyster), leaving it in the shell.
Place the shucked oysters on a bed of crushed ice and serve them with lemon, black pepper or Mignonette Sauce.