If you have never backed up a trailer, you have no idea how confusing and non-intuitive a maneuver it can be. If you want the trailer to turn left, the rear end of your rig must go right and that means cranking your steering wheel right, or clockwise. You gauge your progress by looking in a side mirror, which of course reverses things. So, how does anyone manage it? By going slow, practicing, and frequently taking the truck out of gear and walking around the trailer to see what's happening. Here's some tips from Equipping Your Horse Farm that will help make the maneuver second nature:
Put your hand in the center of the bottom of the steering wheel. If you want the back of the trailer to move to the left, move your hand to the left.
If you want the back of the trailer to go to the right, move your hand to the right.
For a sharp turn, turn the steering wheel before you press the accelerator.
For a gradual turn, turn the steering wheel and press the accelerator at the same time.
Once the trailer is going in the direction you want, you need to straighten out the truck wheels to have your truck follow the trailer.
