Thaw shrimp if frozen (refrigerator or cold running water)
Pat shrimp dry with paper towels
Hold shrimp firmly by the tail
Use a small paring knife to make a shallow cut along the back (top curve)
Lift the dark vein with the tip of the knife or a toothpick
Pull the vein out in one piece when possible
Rinse shrimp briefly under cold water
Pat dry again with paper towels
Repeat for all shrimp