How do I prepare fresh clams for clam chowder?

I regularly prepare New England-style clam chowder with all fresh ingredients except for canned clams which I use out of convenience. I have been feeling guilty of trying to pass my recipe off as "fresh clam chowder" and I want to make it better. I would like to pick up a bag of fresh clams at the grocery store and use these an ingredient.

I basically want to know should I shuck the clams and add them to my soup raw, or should I steam them and pry the cooked clam meat out?