In one exercise, the instructor asked him to pretend he was threading a needle. Gandolfini discovered, to his dismay, that he was unable to do it in front of the class. "I was scared to death. I was shaking," he later recalled.
But he found that the exercises were key to shedding self-consciousness and growing as a performer, allowing him "to get up in front of people and get up and just make a fool of yourself," as he later put it.
His first major film role was 1993's "True Romance," an offbeat crime caper written by Quentin Tarantino and directed by Tony Scott. He played a smiling hit man named Virgil who, in perhaps the most memorable scene, savagely beats a prostitute in a motel room. The scene took five days to film, he later recalled.
But it was his performance as Tony Soprano that made him a bona fide star, not to mention one of the highest-paid actors on TV. By the end of the HBO show's run, he was earning at least $1 million per episode, according to published reports.
After the show ended its run — with a controversial, opaque finale that continues to inspire debate to this day — Gandolfini resisted any temptation to play another mafioso. "I want to get away from the violence a little bit, because it is starting to bother me personally," he said.
He returned to the theater, winning a Tony nomination for his role in Yasmina Reza's 2009 "God of Carnage." He also reeled off a succession of character parts in prestigious films, including last year's "Zero Dark Thirty."
He recently shot an HBO pilot, "Criminal Justice," and completed parts in two as-yet-unreleased movies, a romantic comedy "Enough Said" and the crime drama "Animal Rescue."
His survivors include his wife, Deborah Lin, whom he married in 2008; their daughter, Liliana; a son, Michael, from his first marriage, which ended in divorce; and two sisters, Leta Gandolfini and Johanna Antonacci.
Gandolfini could occasionally be at a loss for words when it came to explaining what made his performances work.
"Standing in public in other people's clothes, pretending to be someone else," he once said. "It's a strange way for a grown man to make a living."
MORE ON HIS LIFE AND DEATH:
Times staff writers Elaine Woo, Steven Zeitchik, Meredith Blake, Greg Braxton, Yvonne Villarreal and correspondent Tom Kington contributed to this report.