It´s pretty self-explanatory, don´t take anything, don´t leave anything - at all.
Even a small rock that might seem insignificant, leave it there. If everyone took a rock, even a mountain would be reduced to rubble. Even a small mint wrapper that seem insignificant, take it with you. If everyone left a mint wrapper, even a massive cave would be filled over-night.
There is however, one exception. Feel free to take as much trash with you when you leave. If everyone took out a backpack full of trash, even a garbage dump could be emptied out easily. Also keep in mind that sometimes even footprints can be damaging. Make sure to avoid fragile areas and be aware of where you step. It´s really quite simple. These exotic sites need to last for generations to come. Don´t ruin them because you´re too lazy to carry your bottles out with you.
On the beach your footprints will not last long before the waves washes them away. This image is made on one of the cleanest beaches in Denmark and it’s not a footprint made by a human; you could call it the footprint of nature. It was really blustery weather on this particular day and the wind transformed the beach into extraordinary patterns of sand.
Leave nothing but footprints, Pakhusbugten, Anholt, Denmark
(Nikon D700, Carl Zeiss ZF.2 50mm 2,0 T* Makro-Planar, iso 250, handheld)