Hi:
You can put a resistor to ground from the signal wire.
Typically, PIR sensors take 45 seconds ~ 1 minute to calibrate. So as soon as power is sent to the PIR, leave the area for a minute so it can calibrate itself. Any humans within its reach will disrupt the calibration. PIR are active-low and will give you a PULSE of 1.
You can limit the scope of the PIR by constructing cylinders or cones around the lense, this will restrict its range. Typically, PIR sense 60 degrees from the radius out.
Other than that just experiment unti you get the perfect conditions for you.
-n