Cracked or chipped shells are a no go ... and a lack of off-putting colors. Clam varieties vary in shade, so don't worry whether it's a grey or orange, but if there's a caught piece of seaweed ...

The clam uses a tiny foot to burrow into the seafloor as it grows. Its shell can end up several feet down, with only its neck poking up into the water. Called siphons, these necks, double-barreled ...