With an estimated fortune of $62 billion, Warren Buffett is the richest man in the entire world. In 1962, when he began buying stock in Berkshire Hathaway, a share cost $7.50. Today, Buffett, 78, is Berkshire’s chairman and CEO, and one share of the company’s class A stock is worth close to $119,000. He credits his astonishing success to several key strategies, which he has shared with writer Alice Schroeder. She spent hundreds of hours interviewing the Sage of Omaha for the new authorized biography The Snowball. 1. Reinvest your profits When you first make money, you may be tempted to spend it. Don’t. Instead, reinvest the profits. Buffett learned this early on. In high school, he and a pal bought a pinball machine to put in a barbershop. With the money they earned, they bought more machines until they had eight in different shops. When the friends sold the venture, Buffett used the proceeds to buy stocks and to start another small business. By age 26, he’d amassed $174,000—or $1.4 mi...