#2

Wait until a friend (or enemy) of yours is out of town.  Then, in the cover of night, string police caution tape around their yard or driveway; utilize trees or road signs to make the caution tape look official.  If time and materials permit: draw chalk outlines of bodies in the driveway or walk.  

#1

Wear a hazmat suit (with a friend or two) and walk around in people's backyards.  For added effect, appear to be taking samples of dirt, rocks, leaves, etc.