There are many different things to look at.
My reasoning is that the cash indexes are the foundation for futures indexes.
But then there is the consideration of what people do to make money in any of the markets.
For me, I try to minimize risk by going second but still a head of the herd.
I feel more comfortable by being "pushed" by people following me into the market. There are herds in all futures indexes and for each equity.
Since everything is moving at all times. Making an assessment about who is going first on what is possible but it does take some clear thinking.
You have to check frequently. Mostly to detemine that nothing in the dynamic has varied from just before. When you see variation in the dynamic balance, you are seeing "smart money" more out in the lead. I keep on the right side of the market by doing what is necessary.
from all the real time sourses that I use, I detect first action from YM, then INDU, and then ES where I trade.
The DJXX definitely lags the YMXX. and DJ s not as excitable as YM.
The SPX.X behaves like INDU and is behind the INDU and unexcitable.
NASDAQ stuff is not attractive to me.
Before open I make segmented "predictions" of all three parts of the market from a long habit going way back to EOD type times. It is always important to "anticipate" the day's action with regard to common moves, mixed moves and divergent moves among all three markets. Knowing this as a context, then, as the market opens and synchs in pairs of cash and futures indexes, you are prepared, in a context, to optimize your trading results in comparison to what is offered to you.
I log this in many market columns by writing in congruent spaces what occurred through the 81 barsof the day (5min). I also create a pictorial path of the ES bar movement. Corny, I supppose, but it's value in terms of what I earn seems to be fairly great.
AMTSWA explained a while back that learning to monitor what is going on in the topic of the thread takes time and is important. You will remember his trading. while many did not grasp the strategy wholly, he had the means and skills to not lock in what looked like losses but on the otherhand really lock in profits. This thread topic is one of the keys to that ability.
I have beginners who can recogonize trends ofdiffering periodicities "building" to concurrent critical turning points. One of the key crushers of this potential elegance is the T Rex person. The market dictates not crude methods. timing is enhanced by what the thread is concern about.