J Welles Wilder has developed the Average Directional Index (ADX) to define trend force, whether the trend will develop further or will gradually weaken.

The simplest trading method based on the system of directional movement implies comparison of two direction indicators: the 14-period +DI (yellow) one and the 14-period –DI (Green). To do this, one either puts the charts of indicators one on top of the other, or +DI is subtracted from -DI. W. Wilder recommends buying when +DI is higher than -DI, and selling when +DI sinks lower than -DI.
To these simple commercial rules Wells Wilder added "a rule of points of extreme". It is used to eliminate false signals and decrease the number of deals. According to the principle of points of extreme, the "point of extreme" is the point when +DI and -DI cross each other.

- If +DI raises higher than -DI, this point will be the maximum price of the day when they cross.
- If +DI is lower than -DI, this point will be the minimum price of the day they cross.

The point of extreme is used then as the market entry level.
Thus, after the signal to buy (+DI is higher than -DI) one must wait till the price has exceeded the point of extreme, and only then buy.
However, if the price fails to exceed the level of the point of extreme, one should retain the short position.