There is a special relationship between clams and tomatoes, and especially among pasta, clams and tomatoes.
Clam sauce goes on top of pasta, usually spaghetti or linguine. Actually, it tastes fine on any kind of "white" pasta, but the long skinny shapes are traditional. Putting on grated cheese is not traditional.
The common varieties of clam sauce are white (no tomatoes) and red (you can probably figure it out). I like them both very much. I've found great clam sauce in many restaurants, and strangely can't think of any favorites. Some "red" sauces are really white sauces with chunks of tomato in them. Some red sauces have red fluid, like marinara sauce.
I like sauces with whole clams (not too tiny) and don't like to bite into garlic cloves that I thought were pieces of clam.
One great way to use stale bread is to sop-up the sauce that remains in the bottom of your bowl.
(Photo above is from Food Networks.)
Zuppa di Clams ( Zuppa di Vongole) is kind of a heavy-duty white clam sauce, without pasta. "Zuppa" means "soup." (Photo at left is from Italianicious.com.