If you leave on vacation, have a key holder visit your house on a daily basis. Criminals look for the following signs:
Dustbins outside long after it was emptied
Outside lights switched on during daytime
If you have a gravel driveway, they inspect it for fresh tracks
A memo was circulated by Nampol stating the following:
Criminals put a piece of chewing gum on the far end of the tracks and return everyday to see whether the gate was fully opened to accommodate a vehicle. This indicates whether a domestic or key holder only opens partially and nobody is there during the night
They also leave a shopping bag with refuse or just a can or bottle on the pavement. They know we clean it up when we are at home. When the same bag is lying there for a day or more they read the signs.