3) Consider international investing
When investors are told to diversify, they instantly think equity and debt. Some will even go a step further and look for a break-down within these categories. For instance, within equity they will attempt to diversify their investments across value and growth, along market cap differentiators, and along sectors and industries. Within debt they will think of a combination of fixed return products as well as debt funds.
The more sophisticated and wealthier ones will move onto higher ground by contemplating along the lines of property, maybe even art and antiques.
Unfortunately, very few think of stepping outside one's geographical boundaries. By ignoring global investing, investors are side-stepping a fair amount of weaponry in their investing arsenal.