First you need to pick healthy clams. Do not buy clams that are chipped, broken, or open. They are alive when you bring them home so make sure you keep them in a cool, open area. Put them in a medium sized container with clean fresh water to soak for 20 minutes. It helps clear out the salt and sand that they store inside. Some chefs say to add a few tablespoons of corn meal to the water to help clean the clams more thoroughly. Pull them out of the water instead of straining them. Scrub the clams, once they have soaked, so you can get all the debris off of the outside of the shell. This process can also be used when you clean mussels.