Morgan Housel a columnist at Motley Fool had a good column in the recent issue of the (WSJ http://online.wsj.com/articles/16-rules-for-investors-to-live-by-1417789469) talking about rules for investors and how to avoid common mistakes. Here he lists the rules:
"1. All past market crashes are viewed as opportunities, but all future market crashes are viewed as risks.
2. Most bubbles begin with a rational idea that gets taken to an irrational extreme.
3. “I don’t know” are three of the most underused words in investing.
4. Short-term thinking is at the root of most investing problems.
5. Investing is overwhelmingly a game of psychology.
6. Things change quickly—and more drastically than many think.
7. Three of the most important variables to consider are the valuations of stocks when you buy them, the length of time you can stay invested, and the fees you pay to brokers and money managers.
8. There are no points awarded for difficulty.
9. A couple of times per decade, investors forget that recessions happen a couple of times per decade.
10. Don’t check your brokerage account once a day and your blood pressure only once a year.11. You should pay the most attention to the investor who talks about his or her mistakes.
12. Change your mind when the facts change.
13. Read past stock-market predictions, and you will take current predictions less seriously.
14. There is no such thing as a normal economy, or a normal stock market.
15. It can be difficult to tell the difference between luck and skill in investing.
16. You are only diversified if some of your investments are performing worse than others."