Scent
When setting up a camera, make sure to touch or disturb as little as possible. Everything that is contacted can leave a scent that the animals will be able to detect. The less that is contacted the better. Use gloves if possible, and don't move around leaves or brush too much.
Placement
Locate an area that is used frequently by wildlife. Look for signs of disturbance or prints. Places where they might drink are also good locations. Place the camera out of sight, and camouflage it with material, netting, or natural items like branches. However, if natural items are used, make sure to use gloves for scent reasons.
Flash
Flash is also something to be considered with a trail camera. It is a useful tool when trying to capture action in the dark. However the wrong flash could scare off animals. Make sure to purchase a camera that has a flash range large enough to cover the area, but not too strong or it will wash out the photo. The manufacture's information can help out by telling the "effective range" of the flash.
Background can also be the deciding factor with a flash. If the area is heavily covered with foliage, the flash is going to be reflected when it hits the background. This will make a weaker flash strong and a stronger one overpowering.
