Start out by selecting a rock that is around 4" x 4". You want it to be big enough to hold down a pile of papers, but small enough to handle. Wash the rock with warm soapy water and let it dry completely.
Tear your decorative papers into pieces around 1- to 2-inches big. Use the foam brush and these decoupage techniques to completely cover the rock with paper pieces. Don't worry about covering the bottom of the rock though. Once you have the rock covered, let the decoupage medium dry. Once it dries, seal your paperweight with a few thin layers of the decoupage medium. Let it dry completely before you move on to the next step.
To finish your paperweight, cut a piece of felt to fit the bottom of your rock. Use craft glue to cover the bottom of your paperweight with the piece of felt. This will protect furniture from being scratched by the rock.
As a finishing touch to my paperweight, I wrote "Imagine" on my rock using white acrylic paint and then sealed it with a few squirts of clear acrylic spray. Enjoy!