Great article by Steven Drobny about Jim Chanos, the well known short seller.
Chanos recommends his fund as an insurance, for all investors who have a sizeable "long" portfolio in shares. Chanos will do well when shares tank, and bad if shares rise. But from time to time there is an industry (for instance property developers) that is badly hit while the overall market rises, in those times both Chanos' fund (shorting that industry) and the overall index can rise.
I normally don't short particular shares (I do from time to time short an index, but only rarely), but even then Chanos' observations are interesting. The way to discover candidates to short is basically the same as the way to discover which shares to avoid like the plague.
Also, observations about China's economy and it's huge property bubble.