I think location is pretty important. Put them down in an area where they have appeared for real previous years. I like a slight rise above the surrounding terrain and have it along a path or grown up logging road helps. Don't forget to locate it under a licking branch. If there are bucks in the area they will find it. Dragging a scent line is always a good way to add to the effect like GTO said. They usually appear in predictable places.