There are two schools of thought.
1)boil crawfish in clean water, then steam in cooler with seasoning
2)season boil water and soak crawfish
no matter what you do, make sure the crawfish are clean. put them in a tub or cooler and rinse them until the water is clean.
Recipe? lots of personal preference required there. get some of the boil liquid OR put half a pound of butter in the water, then a couple onions cut in half, 3-4 lemons and plenty of your favorite boil seasoning.