The two upper charts show the E-Mini contract. The upper one on daily basis and the lower one on weekly basis.
Both charts have an 8 and a 21 average line. The lower windows also show my own TrendMarker indicator.
As you can see, despite the SellOFF last Friday, the upward trend is still intact. The trend can be shown with many possible indicators. Averages are used most often. I like to use exponential averages. Again, you can create a very simple trading system.