If frozen, defrost the packages of crawfish tails. Empty into a bowl and check for any pieces of crawfish that were not properly deveined or look for any pieces of shell. When you're pleased with the crawfish tails reserve them for cooking.
In a sauté pan, melt the butter over low to medium heat. Add the minced garlic in and stir until fragrant. Add the green onions and cook 30 seconds. Add all of the crawfish tails and fold them into the butter mixture.