Get a big pot, and fill it 2/3 full of water (if readily available you may use Ocean Water which is recommended) and bring to a rolling boil on top of the stove. Then, if you are not using Ocean Water, add ¼ cup of salt (per gallon of water) to the water.
Once the water returns to a rolling boil, drop in the live crab. (The crab must be completely submerged in the water, in order for it to cook.)
If your pot is not big enough to fit all of the crab in at once, you may cook them one at a time. Boil the crab for 12 to 15 mins. When crab is finished cooking add to an ice bath to stop the cooking process. (An ice bath is ice with a little water in it, so the ice can move freely in the water.)
To get to the meat of the crab, you must pull the top of the crab off. Once you have pulled this part off, you can clean out all the green/yellowish substance, and pull the lungs off. The lungs are the long skinny pieces that look like meat attached to the center part of the shell.
The meat is located in the legs, claws, and the body of the crab. Pick out the meat and enjoy!