Get low on the ground to get a sense of their viewpoint. Check the ground where you are setting your traps. If you have time, sweep the trail with a switch and reexamine it in the morning you'll learn if the animals are using the trail. Our Tracking video gives a good rundown on tracking pits and other tracking techniques. When you place the snare, attempt to conceal the wire or cord you are using.
Most animals are very quick to identify anything that is out of place.
If you have the option, set traps for large animals like dog or deer. It is more productive in subsistence situations to go after larger game. You get more meat and materials like the hide and bones that can be used. When trapping a larger animal the snare mostly acts to restrain the animal. You need to close in and kill it with a tool of some sort.