When buying clams allow about 6 live clams or 6 ounces of shucked clams per person. If buying hard-shell clams check to make sure they are closed tightly. This is a sign that they are still alive. If the clam is open, tap it a few times. If they do not close by themselves in less than a minute they are probably dead and should not be purchased. If buying hard shell clams tap 2 of them together. They should make a dull thud and not a hollow sound. If any have broken shells do not buy. If buying soft-shell clams the siphon should retract or at least move when you touch it but the shell might not close all the way. If buying shucked clams, the meat should be plump and not smell like ammonia. The liquid should be clear not cloudy or murky. Refrigerate and use them within 24 hours. Live clams can usually be kept for 2 or 3 days. Store live ones in the refrigerator in a bowl covered with a damp towel. Do not store them in water, in a plastic bag or on ice. They need oxygen to survive and the freshwater will kill them. If you are going to freeze the clams, do not freeze them in the shell. Shuck them first. Put them in a container and cover with the extra clam liquor and water. They can stay frozen this way for up to 2 months.
Because the clams spend their lives in the sand they will be gritty if not cleaned. The best way to rid them of this sand is to place them in a mixture of saltwater and cornmeal for a few hours. For every gallon of water add 1/3 cup of salt and about a ¼ cup of cornmeal. Leave them in this solution for 2 to 4 hours, changing the water every half hour. Lift the clams out of the water and scrub them with a stiff bristle brush under cold running water to remove any dirt or particles from the outside.
Place a knife carefully between the two shells and slide the knife towards the hinge until you cut the muscle that holds them closed. Twist the knife back and forth lightly to pry the shells apart. Every task is always easier with the right tool. If you are not experienced opening clams it is a good idea to hold them with a heavy towel or work glove. It’s easy to slip and run the knife into your hand. Here are a few methods to get the clam to open slightly to help enter the knife. 1. Place them in the freezer for an hour and then let them sit on the cupboard for 3-5 minutes. This causes them to relax their muscles and they should open slightly. 2. Place the clams in a 450 degree oven for 3-5 minutes or until they open. 3. Steam them on a rack above boiling water 5-6 minutes until open.
There is a good video that shows how to open clams at http://www.marthastewart.com/904018/v108802-clams-rc2mov.
It’s a good video , but if you are inexperienced I would recommend using a towel or heavy glove to protect your hands.
Tips on how to cook clams