Ask your fishmonger if the clams have been purged of sand. If not, put them in a bowl or bucket of salted water for a couple of hours to ensure they expel all their grit, then rinse under cold running water. Discard any broken clams or open ones that don’t close when tapped on the bench. Use the clams as directed in the recipe.
If the recipe asks for clam meat only, drain the clams and put them in a large pan. Heat until they just start to open, then remove from the heat.
Pull off the top shell and lift out the meat, collecting any juices in a bowl. Strain the juices through a piece of muslin before using.