I ALWAYS take a video of me putting the item I am selling into the final packaging and walking in and dropping it off at the post orifice AND when I buy something take a video of me opening it and noting any damage on the package before opening to make it easier to tell if any damage or wrong missing... was done before or during shipping.

Something funny was one time my dad sent my son a .243 and completely disasembled the rifle through the post office (they told him that was how it had to be done)before packaging it up and sending it to me, when it got here there were huge holes everywhere and the cardboard box was barely hanging on to the rifle butt somehow every single nut bolt and screw and everything was found somewhere in that box!