Warren Buffett didn't become one of the most successful investors of all time by himself. He had mentors, teachers and colleagues that helped him develop his smart investing style over time. People like Benjamin Graham, David Dodd and Phil Fisher helped him develop the tools necessary to build a $92.5 billion empire.
Graham, known as the godfather of value investing, greatly impacted Buffett's investment philosophy when he was his professor at Columbia Business School. Graham and his collaborator David Dodd taught Buffett that successful investors assessed the "intrinsic value," of a business rather than just stock prices.
Buffett himself says his style was 85 percent influenced by Graham and 15 percent influenced by investor Fisher.
In his book "Common Stocks and Uncommon Profits," Fisher famously argues that the best time to sell a stock is "almost never." In Buffett's 1988 letter to Berkshire Hathaway shareholders, he wrote that his "favorite holding period is forever."