Preparation! Every time that I sit at my trading desk, the first thing I do is check to see if the market is trading up or down premarket.  That way I can easily plan ahead.  The market direction usually determine my bearish or bullish position.

The Second Most important thing, is to check any news related items that may affect the stock such as analyst upgrades or downgrades.  I also like to check for IPOs, (those can be tons of fun!)