Warren Buffet in a refresher course on his approach to investing in his 2014 annual letter to Berkshire Hathaway Inc. shareholders.

Fortune magazine published an excerpt of it on line at that time. Fortune writer Carol Loomis, who is a long-time friend of Buffet, edits his annual letter.

The billionaire uses two personal real estate investments he made to demonstrate some of his key principles: focus on what an investment will produce, not its price; stick to what you know; and don’t try to predict what the economy or stock market will do.

“You don’t need to be an expert in order to achieve satisfactory investment returns. But if you aren’t, you must recognize your limitations and follow a course certain to work reasonably well,” Buffet wrote. ”Keep things simple and don’t swing for the fences. When promised quick profits, respond with a quick ‘no.”’

The examples Buffet cited were his 1986 purchase of a 400-acre Nebraska farm and his 1993 purchase of a retail property near New York University’s campus. Both purchases were made after prices collapsed.

Buffet said he didn’t know much about farming or retail, but he knew enough to determine the farm near Tekamah would remain productive and the retail center would keep appealing to NYU students. He also said the largest tenant in the New York property had an under-priced lease that would expire nine years after the deal.

Buffet said he could tell both investments had little downside even though he’s only visited the farm twice and never seen the New York retail property.

Over the years, Buffet hasn’t sought out any price quotes on his farm or retail property, and he isn’t inclined to sell. And Berkshire Hathaway’s chairman and CEO said stock investors shouldn’t be eager to sell just because the market offers them price quotes all the time.

Buffet compared the stock market to having a moody farm investor shout out prices of Buffet’s farm every day. “If his daily shout-out was ridiculously low, and I had some spare cash, I would buy his farm,” Buffet said. “If the number he yelled was absurdly high, I could either sell to him or just go on farming.”

Andy Kilpatrick, who wrote ”Of Permanent Value: The Story of Warren Buffet,” said the essay offers a good summary of the techniques Buffet used to become one of the world’s richest men. “It was a great treatise on value investing,” Kilpatrick said.

Buffet said he learned the keys to investing by reading former Columbia University professor Ben Graham’s book “The Intelligent Investor.” Buffet went on to study under Graham and later work with him.

But for investors who don’t have the skills or time to estimate the value of investing, Buffet repeated his standard advice: make regular purchases of a low-cost stock index fund. “Ignore the chatter, keep your costs minimal, and invest in stocks as you would in a farm,” he said.

Buffet leads the Omaha, Neb., based Berkshire Hathaway conglomerate that owns more than 80 subsidiaries in a variety of industries, including insurance, utilities, rail roads, retail and manufacturing. It also has major investments in such companies as Coca-Cola Co. and Wells Fargo & Co.