I swing trade the Emini and check the TRIN every day. I look for 2 things:
1. Upward and downward momentum in the TRIN that I measure with an oscillator
2. Occasional divergence patterns between the TRIN data and actual price behavior
What I find useful about the TRIN is that there is no price data included in the calculation. So you can use it as a non-correlated market indicator.