The mentality behind short selling is that they are betting on the decline of a stock in terms of the value and they hope to buy it back more cheaply. Short sellers borrow stock and then sell it and this strategy works the best when stock is over valued.
Thus it makes sense to use a combination of tools to arrive at the prediction that whether stock is over valued or not. However do not arbitrarily go by the information available in open media like brokerage houses reports or funds holding state as at times these are released to create a sentiment which is favorable as per their holdings.
You can check out Intraday Short Selling procedure here and do not forget to check the below related posts and we look forward to your comments on the subject that how you have benefitted by short selling or did it cause you a guilt feeling.