Ben Graham's Ten Attributes of an Undervalued Stock

1. Earnings yield (reverse of the PE) that is doulbe the triple-A bond yield
2. PE that is 4/10th of the higherst average PE achieved by the stock in the most recent five years
3. A divident yield of two-thirds the triple-A bond yield
4. A stock price of 2/3 of the net current asset value (those assets that are immediately convertible into cash)
5. A stock price of 2/3 the tangible book value per share. This is calculated by adding up all the assets, excluding intangibles such as goodwill, patents, etc..., substracting all liabilities and dividing by the total number of shares out.
6. Total debt that is less than tangible book value
7. A current ratio of two or more (a current ratio is current assets divided by current liabilities)
8. Total debt less than the net current asset value
9. Earnings that have doubled in the most recent ten years
10. No more than two declines in earnings of 5% or more in the past ten years

The first litmus test (as outlined in the Intelligent Investor) PE * BV/Share <= 22.5. If it's below that threshold look further...