To maintain Tony’s "simmering rage," Gandolfini would often place a small stone in his shoe to stay genuinely irritated during a scene. For groggy breakfast scenes, he would sometimes stay awake for 24 hours to achieve an authentic look of exhaustion.
Showrunner David Chase was notorious for his meticulous control. Nothing made it onto the screen without his approval, from the scripts to the specific shade of a set wall. The Sopranos: Behind-The-Scenes
Actors were strictly forbidden from changing even a single word of the dialogue. If an actor felt a line didn't fit their character, it led to a long discussion with writers, but Chase almost always insisted it stay exactly as written. To maintain Tony’s "simmering rage