"Clam" is a generic name for a dozen or so different bivalved sea creatures who dig themselves into the sand. Hard-shell clams, such as littlenecks and quahogs, are often served raw. Soft-shell longnecks and steamers have a more delicate shell and are served cooked.

Although they don't have a beard (like mussels do), clams do need to be cleaned and soaked before cooking. Scrub them with a stiff brush and then add some cornmeal to the water in which you soak them.

Eat clams as soon as possible after they've come out of the sand. If you do need to store them, keep them in a refrigerator, in a bowl covered with a damp towel.
 
If a clam opens before you cook it, tap on the shell. If it closes again, it's fine. If not, toss it. When exposed to heat, clams relax the muscles that hold their shells together. So be sure to toss any clams that don't open naturally with cooking.

Find out more by reading Root Source: Clams