The following graph gives an illustration of investing a dollar in different asset classes in the market from 1926 to the end of 2007. The returns and dollar value shown represent past performance only and does not guarantee future results. The red arrow at the bottom indicates when 9-11 occurred. (Photo credit: Wikipedia)

1. Understand What Type Of Investor You Are

A key principle is to understand what type of investor you are. There are either active or passive investors. To be an active investor one must be committed to doing the necessary research in order to generate a good return. They also must learn to manage risk wisely. A passive investor does not have the amount of time it takes to properly research and diversify investments. This type of investor is better off investing in a whole index fund where they can achieve diversity and get the return of the whole index. Another option is to let a professional handle his investments if they do to have the time to devote to it.