Asset Allocation by Age

This one really isn't a math trick, so much as it is a rule of thumb ...

The Trick: Don't have a financial planner to walk you through asset allocation? A simple way to find out is to subtract your age from the number 120; the number remaining is the percentage of your portfolio that should be in stocks.

Example: For instance, if you're 50, you should be keeping 70% of your holdings in stocks with the remaining 30 percent in fixed income products.

The basic idea here is that younger investors who have decades of working ahead of them can take on more risk than people closer to retirement.