docs: update README

Author: markuslf

check-plugins/sensors-battery/README.rst

@@ -4,7 +4,11 @@ Check sensors-battery
 Overview
 --------
 
-Return battery status information. If no battery is installed or metrics can't be determined OK is returned.
+Return battery status information. If no battery is installed or the metrics cannot be determined, 'OK' is returned.
+
+Hints:
+
+* Run ``sensors-detect --auto`` beforehand to scan your system for the various hardware monitoring chips or sensors supported by libsensors or, more generally, by the lm_sensors tool suite.
 
 
 Fact Sheet

check-plugins/sensors-fans/README.rst

@@ -4,7 +4,11 @@ Check sensors-fans
 Overview
 --------
 
-Return hardware fans speed. Fan speed is expressed in RPM (rounds per minute). OK if no fans are found.
+Return the speed of the hardware fans. Fan speed is expressed in RPM (rounds per minute). The plugin returns 'OK' if no fans are found.
+
+Hints:
+
+* Run ``sensors-detect --auto`` beforehand to scan your system for the various hardware monitoring chips or sensors supported by libsensors or, more generally, by the lm_sensors tool suite.
 
 
 Fact Sheet

check-plugins/sensors-temperatures/README.rst

@@ -4,7 +4,11 @@ Check sensors-temperatures
 Overview
 --------
 
-Return certain hardware temperature sensors (it may be a CPU, an hard disk or something else, depending on the OS and its configuration). All temperatures are expressed in celsius. Check is done automatically against hardware thresholds. If sensors are not supported by the OS OK is returned.
+Certain hardware temperature sensors may be returned (it could be a CPU, a hard disk or something else, depending on the operating system and its configuration). All temperatures are expressed in Celsius. Checks are performed automatically against hardware thresholds. If the sensors are not supported by the OS, 'OK' is returned.
+
+Hints:
+
+* Run ``sensors-detect --auto`` beforehand to scan your system for the various hardware monitoring chips or sensors supported by libsensors or, more generally, by the lm_sensors tool suite.
 
 
 Fact Sheet