Passive InRrared sensors:
NOTE:Most of the time pin configuration will be printed on the sensor . But some sensors available with in in India are not describing pin configurations properly. But the standard notation of pin will be like all ways middle pin will be output. so if you identify the GROUND then remaining pin will be VCC.
It is very simple. Most of these sensors are made of using BISS0001(16 pin DIL package). 7th pin of this IC is GND. So take a multimeter and check for short circuit test and beep sound. then it will be your sensor ground and opposite side pin will be VCC