What is the proper care for shellfish after harvesting?

Once you've got your shellfish, you want to keep them alive until you're ready to prepare them.  NEVER eat shellfish that have died before you've prepared them.

To keep the animals alive, keep them cool and out of water.  If they are stored in water they could use up all the oxygen and suffocate.  Place your shellfish in a container under damp material (seaweed, towels, etc.) and keep them in a cool place.  If you store them in the refrigerator, keep them in the crisper so they won't dry out.  Inspect your shellfish before preparing them, if they're gaping touch them to see if they close up.  If they don't close, they are not safe to eat and should be discarded.  

In anticipation of eating your shellfish you might want to scrub the shells clean.  Some people like to purge their shellfish prior to preparation.  To do this, put the animals in a clean bucket of seawater (adding cornmeal to the seawater is thought to make them sweeter)  and allow the animals to feed for about 1 hour.  Use an air bubbler, if available, to help maintain the oxygen level in the water.   IMPORTANT: Don’t use tap water – this will kill them.