It's a sad week for skeptical investors as MarketWatch columnist Herb Greenberg has delivered his last column for the site. He is leaving Dow Jones to start his own research firm.

For his last piece, Greenberg offers readers parting advice. I would suggest printing the column out and consulting it before making your next investment. Following these tips won't help you avoid every bad investment, but it'll probably eliminate most.

Greenberg's tips are these: the numbers don't lie -- pay attention to the numbers and ignore the narrative. Greenberg writes that "some short sellers and forensic analysts don't like to talk to companies. They want to avoid the spin or the face-to-face meeting that can create a psychological connection that may skew what otherwise would be black-and-white analysis. Don't ever underestimate the power and influence of the human factor."

Greenberg also suggests paying attention to quality of earnings, understanding the flexibility that exists within GAAP, and -- this one might be a little trite but it's still true -- not confusing stocks with companies. Greenberg also urges investors to "instead of asking how much you can make, first ask how much you can lose. That is what the smart guys do."

Although he's been the brunt of a lot of vitriol from conspiracy theorists and investors in bad companies, Herb Greenberg has been right more often than not -- which is a lot more than can be said for just about any other financial journalist.