I always aim mine right down the trail. You will miss alot of deer if you put it at a 90degree angle. If they are walking fast or running they will be by it before it triggers. By aiming right down the trail it gives your camera plenty of time to sense the deer coming and get the pic off.

If you look at pictures of deer cam pics of deer running, the deer is always coiming right at the camera. Not left to right vice/versa. Not that you won't get one like that but you give yourself a better chance by aiming it down the trail.