You can use one or more of things like these: plastic peanuts, broken-up pieces of styrofoam from another package, tightly balled-up newspapers, extra foam plucked out of a carrying case. Staples sells the peanuts in big bags, overpriced, but you can scout out retail stores for stuff they're discarding. Sometimes they'll just give it to you, other times its in/near their dumpsters.
Get one sturdy cardboard box that's about 6-10 inches bigger in all dimensions than the camera. Add a layer of packaging material, then the camera, then fill all around with packaging. Seal the box with tape. Shake box to make sure there's no movement inside.
Take another box that's about 1 ft. bigger all around than your first box, add layer of pkg matl, add box, stuff all around and top with more pkg matl. So you have a shock-insulated box within another. Shake to check for movement.
