If you follow the money, as in many things, you will see a valuable leading indicator. Since there is more money changing hands in the S&P futures pit (and eminis) than the rest of the overall market, it only makes sense to follow the Spoos. When there is premium to FV, the market will follow, when there is a discount to FV, the market will follow (downward). If you add the $$ involved in program trading, then you have an even stronger leading indicator.
When it comes to using certain issues (as INTC, mentioned above), be a bit careful...it can work because many traders jump to a "favorite stock" then jump aboard with or to hit on the down side. Because underlying factors (support, resistance, dividend yields, and institutional buying/selling) affect individual issues (as opposed to the entire market), the use of single stocks is not as reliable overall.
The S&P traders watch the bonds until they close at 3PM, and then you will see a bit of market "free-for-all" while the traders settle into the day ending pattern.