How I clean Pismo clams

Set the clam up on it's end, so you can approach it from the top.

You want the clam to be open a bit. 

Take a large knife, and cut straight down with the knife, splitting everything in two, and cutting the large adductor muscles on either side of the clam. If the clam closes on you before you get all the way cut, take all small knife into each side to cut the adductor muscle.

Once cut, open the clam, and let it drain the "clam juice" into a bowl for a few minutes.

After it's drained, you should have something like this. Adductor muscles are marked with arrows.

The next step is to remove the meat from the shell. It will be attached around the mantle, the long edge away from the hinge. Then detatch the adductor muscles from the shell. There will a a couple of places near the hinge that will be connected, as well as a little bit of attachment in the middle.

Attachment points noted

Now for the cleaning. Supposedly the whole clam is edible. But for aesthetics, and ickyiness, I like to remove anything dark that could be sand or the clam's digestive system. Here's most of the stuff I remove, labeled. 

For Clam Strips, I usually cut the foot into bite sized pieces, then use the rest of the clam for chowder or fritters.