Actually I would cook the shrimp in the shell and then plunge into cold water to stop the cooking process. Shrimp cooks really fast and out of the shell it will turn to mush. So, once it's chilled in the ice bath start your peeling. I will politely disagree with Steve A here in that 8 minutes is way too long for pre-peeled shrimp. More like two or three minutes. De-veining is a matter of personal taste, but easier to do after cooking.

Once shrimp is shelled and deveined - bring water to boil with onion, celery, parsley - what have you have in the fridge as a base. once boiling - add shrimp - cook 8 minutes. Drop in ice bath to cool. This can be made the day before.

Cocktail sauce; ketchup - horseradish - lemon juice - drops worcestershire sauce