Here's what I do for a sack of about 35 lbs. I use a brand of seasoning call 'Cajunland' (google it). There are many others but I like theirs best.
I add a large box of that seasoning, 6 onions cut in half, 6 lemons cut in half and the juice squeezed into the water, 8 whole bunches of garlic, cut in half and added, 4 stalks of celery, 1/4 box of salt, Tabasco suace or cayenne pepper to taste (I don't use too much if I have out of towners eating) and 2 handfuls of bayleaves (fresher the better). Sometimes I add worstershire sauce.
Bring just about 1/2 of the larger keg of water to a boil and cover and let and add your potatoes. Let boil for 5 minutes and add the sack of crawfish. Stir and cover and let come to a boil. When the boil starts, only boil for 2 minutes and shut off the heat. Leave covered for 15 minutes then stir and cover for 10 more. Then I start tasting them to see if they need to sit more. Sitting covered is very important.
If you want corn, add them as soon as you turn off the fire. Some folks put sausage in their crawfish. I find it messes up the flavor so you can always take the crawfish out of the boil water, then add the sausage or artichoke or whatever you want to try, to the water and heat again. Warning, whatever you add will be extremely salty.
