The Dow Jones Industrial Average is an index composed of 30 stocks. IBM XOM BA MO MMM UTX PG JNJ CAT KO make up just under 50% of the index. These 10 stocks lead the Dow up or down. If these stocks start gaining strength, it is almost a certainty that the Dow will too and vice versa. Keep an eye on the movement of these stocks and you can time the Dow intraday. Today for instance, IBM is up nearly 6% in premarket. IBM is 6.76% of the Dow. XOM is up over 1%. XOM is 5.61% of the Dow. MO (5.1% of the Dow) is up 1.5%. PG (4.55%) is up 1%. Just by keeping an eye on these major components one can see that the Dow will be very strong to start the day. If strength holds among these top 10 names, its likely the Dow will have a strong day.
The same study can be done with the S&P 500 by breaking down its components. Some of the S&Ps biggest names are also part of the Dow - XOM GE MSFT T PG JNJ . Throw in CVX BAC MO PFE CSCO AAPL IBM GOOG AIG JPM C KO MRK VZ and you have the top 31% of the S&P 500. 20 stocks in total. Many of these names are also up strongly in premarket - GOOG AAPL CSCO BAC JPM apart from the Dow names we mentioned before. So again I expect the S&P 500 to start the day of very strongly and as long as these big 20 stocks stay strong, its likely the S&P will have a strong day.