An espresso is only as good as its maker. A conscientious espresso maker will strive to use the best beans, ground to the proper consistency in a good machine.
Cleanliness is a very important factor. Residue from old grinds will contaminate the flavor, producing a mediocre to lousy espresso. Grinders should be thoroughly cleaned at least weekly, using a stiff brush like a toothbrush or stiff bristle paintbrush to clean the grinding plates, and a clean soft rag to wipe down all parts. NEVER use water to clean an electric grinder! Espresso machines should be thoroughly cleaned daily, or immediately after use to prevent a buildup of oils that could affect flavor.