When Tracy Britt Cool was finishing Harvard Business School, she wrote to Warren Buffett to ask for a job. Less than five years later, she's among Buffett's top aides atBerkshire Hathaway (BRK/A), where she oversees subsidiaries with more than $4 billion in annual sales and more than 10,000 workers. “She thinks like I would,”Buffett tells Noah Buhayar and Laura Colby in this week's Bloomberg Businessweek.

Some of the attributes that helped Cool rise aren't easily imitated. She developed a work ethic growing up on her family's farm and was voted most likely to become a billionaire by high school classmates in Manhattan, Kan. Then she was one of eight students from her class at Harvard University accepted directly into HBS from the undergraduate program. Here are four of Cool's more easily adopted habits:

Be a joiner … During her sophomore year at Harvard, Cool led fundraising for the Harvard Undergraduate Women in Business, served as an executive board member of the Women's Leadership Conference, and was also a member of Kappa Alpha Theta, according to Buhayar and Colby. One of her college internships was at 85 Broads, a network that promotes women business leaders. Learn Cool's remaining three easily adopted habits.