When you bring to home, put them in an ice chest leaving crawfish in sack with a layer of loose ice on the bottom and on top of crawfish.  Close the ice chest lid, unplug the ice chest and tilt so that any excess water drains out to last overnight.    Replenish ice as it melts. The loose ice also allows crawfish to regurgitate dirty water, puts them asleep and keeps them moist; or you may keep crawfish in walk-in cooler off the ground at approximately 38 to 42 degrees with wet towel on top.  This applies for live crabs also.  Use the same ice chest before boiling, add water and let soak for about 5 minutes after closing plug.  Drain ice chest and boil.  Do not put in tanks or use salt to purge.