Hard-shell crabs are best boiled whole. Grasping a live crab from the back or with tongs, rinse it in cold fresh water, then drop it into boiling salted water seasoned with your own combination of spices or with commercial crabboil seasoning. When the water returns to a boil, continue cooking for 20 minutes (25 to 30 minutes for Dungeness crabs), then drain.
To eat a crab, lift off the apron-a circular shell segment on the female’s belly, a pointed section on the male’s and pull off and discard the entire top shell. Pull out and discard the long, whitish gills and the spongy stomach.
Bend and snap off the claws. Snap the body in two and remove the meat with a nutpick or your fingers. Crack the claws with a nutcracker or wooden mallet and pick out the meat.
Soft-shell crabs (hard shells at the molting stage) can be broiled, sauteed, or deep-fried. In all cases, they must be killed and cleaned first; you can usually have this done at the fish market.
To kill a soft-shell crab, grasp the body between the back legs, and cut across its body just behind the eyes with kitchen shears. Reach into the cavity created by the cut and pull out and discard the stomach. Pull off the apron. One at a time, fold back each side of the top shell and remove and discard the gills, but don’t remove the shell. Wash the crab and dry it.
To saute a soft-shell crab, flour it lightly and brown it in butter for 3 to 4 minutes over moderately high heat. Sprinkle it lightly with salt and pepper. Eat the entire crab, shell and all.