Stand still. The moment you realize that you need to get past a motion detector, stop where you are and gain your bearings.
Locate where the motion detectors are. Keep in mind that some detectors can be placed opposite each other to fully cover an area or a hallway. They are usually mounted in the high corners of rooms, pointing toward doors and windows.
Retrace your steps backward, following the exact way you came. If you need to take a new route, identify all visible detectors before proceeding.
Stay close to the walls on which the detectors are placed. Most detectors have blind spots directly underneath, so the wall on which they're mounted is virtually invisible to them.
Move slowly and stay low along that wall. The lower you are, the more out of reach you are from the motion detector's line of sight. Watch for other motion detectors that may be facing in the opposite direction.
Crawl across open spaces. Some motion detectors are designed with special "pet alleys," leaving room for smaller four-legged animals to pass safely underneath the line of sight. Try to stay lower than the average-size dog.
Cover the faces of the motion detectors with a piece of paper or cardboard. This is not a foolproof method -- it is simply a last resort. Very slowly move the obstruction in front of the detector's sensor and attach it gently.