Customer Service Jellies: What's the best course of action to take when you are fed up with a company/business?

Who/what/where does one complain when having issues with a large company like AT&T, DishNetwork, etc.? To the company via email? The BBB? Is this ever effective?

Any former/current customer service folks have any tips?
It’s so frustrating to not be able to punch bigwig CEOs directly in the face, ya know?