Respect the negative and unknown: Focus on arguments counter to your thesis and be aware that your assumptions about the future are likely going to be wrong.
Avoid macroeconomic bets: Don't make an investment that will suffer severely if the economy or commodity prices move against it.
Think independently: Form your own opinion about what an investment should be worth based on its fundamentals, regardless of who else has invested in the same security.
Be patient: Even if you have spent months researching an investment, be ready to take a pass if you discover something that no longer makes it attractive.
Be selective: Conduct thorough research and only invest in securities with return profiles that you are comfortable with. Don't diversify for diversification's sake.