Before you boil the crawfish, you must first purge them. Place the live crawfish in a bucket and cover with water and add salt. Stir a few minutes then rinse. Do not leave them covered too long or they will die. In a large pot, filled with water on high heat, add crawfish boil to the water. Cover and let the water come to a roaring boil. Add the vegetables (potatoes, corn, mushrooms, onions) and let boil until the potatoes are done. Now comes the fun part, allow the water to return to a roaring boil and add the crawfish for about 5 or 6 minutes, then removed from heat, keep the lid on and let the crawfish absorb all the seasoning for about twenty minutes. Drain and dig in.