Before discussing Guy Spier's precepts, it's important to remember that he not only emulated Warren Buffett's style on the markets, but also his lifestyle habits. To keep a cool head, avoid being influenced in his decisions and preserve an independent spirit from Wall Street, Guy Spier moved from New York to Zurich, just as the Oracle of Omaha isolated himself in Nebraska. Finally, it's worth mentioning that Guy Spier's advice is not a set of investment rules, but rather a set of behavioral rules designed to keep you from getting distracted by others.

1) Stop watching stock prices

When it comes to long-term investing, paying too much attention to market movements can make you want to act on your positions. He believes that most of these buy or sell decisions will be wrong, as they will be influenced by your emotions and price movements, rather than by a cold analysis of the company.

2) Don't buy what someone is trying to sell you

This is a basic rule that may apply outside the financial world, but Guy Spier hammers it home: he doesn't listen to people who are going to pitch him an investment idea.

3) Don't talk to management, don't listen to company management

It's a rule that many managers, fond of talking to CEOs or CFOs, don't share, but Guy Spier reminds us that managers are excellent salesmen, that they are naturally optimistic for having reached their position, and that they will tend to embellish their company's situation, even unintentionally.

4) Do your research in the right order

Here again, it's important to avoid influence. If Guy Spier wants to form an opinion on a stock, he starts with the least biased information: financial publications and quarterly results, then the auditors' letter, then the accounts (to make sure they're valid), then the annual reports and the management's introductory letter, which already belong to the world of corporate communications. Finally, he concludes with press releases, conf calls and newspaper articles. He points out that he avoids reading financial analysts' research when he hasn't yet formed an opinion on a stock.

5) Don't discuss your investment ideas with people who have or had a position in a stock.

People who have made or lost money on a stock are not neutral, and their liabilities may influence your opinion.

6) Never buy or sell stocks when the market is open

According to Guy Spier, decisions should be made outside stock market opening hours. Borrowed from Mohnish Pabrai, this rule means not letting your brain be influenced by the market's movements.

7) If a stock collapses after you buy it, don't sell it for two years.

This surprising rule, also borrowed from Mohnish Pabrai, only applies to investors who carry out thorough research before investing. The aim is primarily psychological: an investor is much more cautious in his choices if he risks being stuck with a stock for 2 years. This rule requires excellent knowledge of the company and a very strong conviction about your decision.

8) Don't talk about your investments

Guy Spier explains that talking publicly about your investments risks undermining your convictions. This is known as commitment bias: if you tell your family you're going to run a marathon in three months' time, you're more likely to go through with it than if you don't tell anyone, in which case it's easy to give up. In investment, Spier believes it's much freer to change one's mind about a company or another.

Obeying all these rules will ensure that the investor is not influenced by his environment, the news or those around him. If the book had been written today, it's highly likely that Guy Spier would also be advising investors to stay away from social networks.