Millions of investors chase Warren Buffett. Tens of thousands attend Berkshire Hathaway's annual shareholder meetings. Wealthy fans bid millions of dollars to have lunch with him. His appearances on CNBC bring trading floors to a halt. People want to know what he's thinking. Why he's different. What secret has made him so much more successful than anyone else.

What's interesting -- and a little ironic -- is that Buffett has never held back what his secret is. As he recently told PBS:

I read a book, what is it, almost 60 years ago roughly, called The Intelligent Investor and I really learned all I needed to know about investing from that book, and in particular chapters 8 and 20. ... I haven't changed anything since.

One book. Two chapters. Legendary success. 
You'd think such precisely guided advice would draw more attention. Not only has Buffett filtered his success down to one book, he has even listed the two specific chapters on which he built his wisdom. He's making this almost embarrassingly easy for us.

What bits of sage advice do these two chapters -- published in 1949 by Buffett's early mentor Ben Graham -- hold? Here are key points from each one. 

Chapter 8: The Investor and Market Fluctuations 
Markets go up. Markets go down. Most of us accept this fact until we experience the latter, at which time we throw up our hands and consider the whole thing a sham.

That kind of behavior is what Chapter 8 is all about: dealing with market movements, and how fundamental they are to investing success.

We have a tendency to become confident and invest the most money after stocks have logged big gains, and vice versa -- selling in a panic after big drops. Two seconds of logical thought will tell you this isn't rational. Yet we do it over and over again.

Buffett built his success on exploiting the market's movements, rather than following them with lemming-like obedience. He bought stakes in companies like Johnson & Johnson (NYSE:JNJ) and Wells Fargo (NYSE:WFC) earlier this year when the market wanted nothing to do with them. He sits on his hands while companies like Apple (NASDAQ:AAPL) and Baidu (NASDAQ:BIDU) go ever higher, ignoring heckles about his technophobic incompetence.

It's truly as simple as "being greedy when others are fearful, and fearful when others are greedy." Here's how Graham puts it in Chapter 8:                          

The true investor scarcely ever is forced to sell his shares, and at all other times he is free to disregard the current price quotation. He need pay attention to it and act upon it only to the extent that it suits his book, and no more. Thus the investor who permits himself to be stampeded or unduly worried by unjustified market declines in his holdings is perversely transforming his basic advantage into a basic disadvantage. That man would be better off if his stocks had no market quotation at all, for he would then be spared the mental anguish caused him by other persons' mistakes of judgment.

Chapter 20: Margin of Safety as the Central Concept of Investment 
Graham opens Chapter 20 with a potent message:

In the old legend the wise men finally boiled down the history of mortal affairs into the single phrase, "This too will pass." Confronted with a like challenge to distill the secret of sound investment into three words, we venture the motto, MARGIN OF SAFETY.

We have an overwhelming urge to expect certainty, but live in a world that is anything but certain. Forward-looking projections of a stock's value are based on assumptions, prone to wild miscalculations and unforeseen events. And by "prone to," I mean "100% assured of."

There's only one surefire solution to this: Pay far less for stocks than your estimate of value, leaving room for error. That's a margin of safety. It's giving yourself room to be wrong, knowing that you probably will be.

Think Ford (NYSE:F) is worth $10 a share? Great. Don't pay more than $5 for it. Think UnitedHealth (NYSE:UNH) will earn $3 per share next year? Wonderful. Set yourself up so you'll do fine if it makes only $2 per share. There has to be a wide range of acceptance between the projected and the potential.

One stock that might epitomize the opposite of a margin of safety is Caterpillar (NYSE:CAT). On hopes, dreams, and expectations that the housing crash may be petering out, shares have nearly tripled since March. 

Granted, the market was anticipating the apocalypse back then. But today's price values shares at fully 22 times next year's earnings estimates, and still 16 times 2011's estimates. 

That might seem reasonable to an optimist, but we have to ask: What happens if the building recovery investors seem to be anticipating never takes place? What if the housing crisis drags on for another five years? What if another leg of the credit crisis halts commercial building? On that note, isn't it fair to assume commercial real estate will almost certainly be face-down in the mud for the foreseeable future? 

Crazier thoughts have been proposed, dear Fools. And it makes Caterpillar -- in general a great company -- lack the level of safety a value investor should demand from a great stock.                                        

Moving on 
These lessons might seem basic and dull. They are. Yet too many investors fail to implement them. Buffett obviously isn't the only one who's read The Intelligent Investor – he has simply put its lessons and theories to work in a habitual manner.

Our Motley Fool Inside Value team strives to put these basic values to work with all of its recommendations, which are outperforming the market by an average of more than six percentage points each. To see what we're recommending right now, you can try the service free for 30 days. Click here for a free report. There's no obligation to subscribe.

Already a member of Inside Value? Log in at the top of this page.

This article was first published on July 17, 2009. It has been updated. 

Fool contributor Morgan Housel owns shares of Berkshire Hathaway and Johnson & Johnson. Apple, Berkshire Hathaway, and UnitedHealth Group are Motley Fool Stock Advisor selections. Berkshire Hathaway and UnitedHealth Group are Inside Value selections. Johnson & Johnson is an Income Investor recommendation. is a Rule Breakers pick. The Fool owns shares of Berkshire Hathaway and UnitedHealth Group, and has a disclosure policy.