I recently wrote an article in which I briefly outlined a couple of investment ideas, Tarragon (NASDAQ:TARR) and Valassis (NYSE:VCI), that I thought were interesting, and which investors might find worthy of some due diligence before making a buy or sell decision.

Due diligence typically entails reading the last three to five years' worth of annual reports and other financial statements, talking to management, and checking out newspaper or newsletter articles, analyst write-ups, industry sources, and whatever other information is out there. This process can take 20 to 50 hours or more. Some analysts take this a step further and personally visit management, or engage in other tactics -- such as counting cars at a retail store's parking lots -- to get a sense of how well business is going.

Because readers have busy lives and look to places like The Motley Fool for guidance in their investment decisions, I intend to highlight only those investment ideas on which I have already completed the due diligence process. I'd also like to suggest to readers that an hour of due diligence can uncover some key issues.

A reader sent me this link concerning Tarragon's CEO, William Friedman.

It appears Friedman was once involved with some questionable characters such as Gene Phillips, Michael Milken, and Charles Keating. Phillips and Friedman ran a REIT called Southmark that eventually went bankrupt in 1989. Although some would consider this ancient history and argue that Friedman has built Tarragon into a respectable company (Friedman and Phillips had a falling out in 1992), others might be a bit wary. As for me, I still haven't done enough due diligence to pass judgment; however, I suggest readers engage in a bit of their own "due dilly" to make a more informed decision. After all, nothing is more satisfying than a correct "buy" or "sell" decision based on one's own analysis.

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Fool contributor Emil Lee is an analyst and a disciple of value investing. He doesn't own shares in any of the companies mentioned above. Emil appreciates comments, concerns, and complaints. The Motley Fool has a disclosure policy.