Just follow these simple rules that everyone agrees upon:
1. definitely use ice after you boil them to cool them down
2. definitely do NOT use any ice, that is a 'waste' of ice
3. season the water before you cook them
4. season the crawfish after you boil them
5. do NOT season the crawfish after you boil them
6. throw them in the cooler after you boil them
7. do NOT throw them in the cooler afterwards because that keeps them cooking
8. Purge them with saltwater before you cook them
9. do NOT 'waste' your time trying to purge them with salt as that does nothing. Time is the only thing that truly purges them
10. place (insert any random ingredient here such as butter, vinegar, beer, etc.) in the water as it makes the crawfish easier to peel
thats all I can think of, but no matter what, you will somehow be doing it wrong and if anyone is there watching you they will let you know