In order to maximize the security function of your motion lighting, make sure to place the lights to cover any approaches to your house and yard, including darker areas of your yard, around trees and bushes near your house, at fence gates and patio doors. These measures won't guaranty security, but these lights provide cost effective ways to scare away potential intruders, and let you know when there is movement in and around your home at night.
Installation Height Consideration
Motion lights best detect motion (through heat) from movement across the sensitivity detection zone, rather than motion that is moving directly towards the sensor. Keep this in mind when placing your lighting. Also, placing your motion detector lights approximately 6 to 10 feet above the ground will help you best pick up motion across the sensor, instead of motion directly toward the sensor.
Use of Existing Non-Motion Lighting
If you are using existing non-motion lighting, and adding a motion detector to these lights, then you may not have the flexibility to give you best security and convenience in these existing light positions. Keep in mind that you can buy remote motion detection units that you can mount at a distance away from the light itself, to give you flexibility in placing the motion sensor to give you best use. The wires that you run from the light to the motion detector are low-voltage, and as a result don't require special plastic or metal protection conduit when you install them.
Taking a little bit of time to plan your motion lights around you home will pay off in terms of the benefits you receive from your lighting. Make sure to consider your home layout, your yard layout, your primary reason for the motion lighting, and any existing limitations (whether from existing lighting or electric wiring issues) that you may encounter when installing your lighting. A little extra up-front planning will help you maximize the security and convenience functions of your lighting!