This technique can turn out some really interesting and eye-engaging work.
1.) Either lightly draw with colored pencil or graphite. Alternatively skip the sketching altogether and apply pigment straight to the wet paper. Move onto step two if you're going to go straight to the paper.
2.) Wet the whole surface of the paper using a wide brush.
3.) Apply pigment (watercolor or gouache) onto the wet paper surface. It is okay to have pools and lakes.
4.) Pour salt on top of the pooled water and pigment. The salt will absorb and draw the pigment toward itself. These will create veins and crystallographic fractal forms that look a lot like branching trees and ice.
5.) Use a ruler and exact knife to crop and cut your work from the paper. Photograph areas of the most interest. Use these studies for all kinds of things from film stills to backgrounds, or even to draw on top of with other media (like colored pencils, or even paint)!