1) Have 6 months of expenses in cash investments.
2) Pay off all credit cards before investing.
3) Stocks go down after you buy them.
4) Stocks go up after you sell them.
5) You will never buy the best mutual fund of the year.
6) You should never buy last year's best mutual fund.
7) You will think your friends are doing better than you.
8) Your friends will not tell you about their losers.
9) Don't invest in a company if you don't know what they do.
10) If you saw the news on CNBC or in Businessweek, it's already too late too act.
Bonus Rule: Stocks don't care at what price you bought it, the chart is going to do what it is going to do, regardless of your cost.