Linear Regression Slope   

The Slope shows how much prices are expected to change per unit of time. Slope gives you the general direction of the trend (positive or negative), r-squared gives you the strength of the trend. A high r-squared value can be associated with a high positive or negative Slope.
When the Slope of the trend first becomes significantly positive, you could open a long position. You could sell, or open a short position when the Slope first becomes significantly negative.
You may even consider opening a short-term position opposite the prevailing trend when you observe the Slope rounding off at extreme levels. For example, if the Slope is at a relatively high level and begins to turn down, you may consider selling or opening a short position.
The Linear Regression Slope indicator provides the slope at each bar of theoretical regression lines, which involve that bar and the previous N-1 bars (N being the regression period). 
First, the data, based on the price selected, is smoothed using the moving average period and type (specify a period of 1 if no pre-smoothing is desired).  The resulting data is then used to form regression lines ending at each bar, using the regression period specified.  The slope of each bars regression line is the recorded as the linear regression slope value for that bar.
Usage:
The Slope shows how much prices are expected to change per unit of time. It gives the general direction of the trend (positive or negative)