Do not open clams until ready to serve raw or to cook. Soft-shell clams must always be cleaned. Hard-shell clams may be immersed in salt water for at least 20 minutes to eliminate any sand or grit; however, many chefs believe that this soaking results in the loss of flavor. Scrub the shells to clean off any debris that clings to them.
To open, hold the clam in one hand protected with a clean, folded kitchen towel and place the sharp edge of the clam knife into the crack between the shells. Squeeze with the fingers of the hand that is holding the clam and force the knife between the shells. Taking care not to damage the soft muscles against the lower shell, carefully slide the knife against the top shell to cut the adductor muscle to loosen the clam completely. Discard the top shell. If serving raw, keep the clam in the bottom shell. Carefully brush away any loose particles of shell that might be left in the remaining shell.