When building constructions with corrugated cardboard consider the direction of the corrugation. With the corrugation perpendicular to the load, it is able to hold a tremendous amount of weight. At the same time, it is hardest to fold against the corrugation.
Folding the cardboard as little as possible allows for the greatest amount of strength. So a triangle tube would be stronger than a square or cylindrical tube.
hot-glue is the glue of choice when working with this. It's speed and great strength make it ideal for quicker structures.
Folding the cardboard against the corrugation is often tricky. By dragging the back of a utility knife along the line you wish to fold will crush the corrugation in that spot allowing for a very clean fold. You may need to make several passes to make the fold easy, but just be aware that you do not want to cut or rip into the cardboard.
Cardboard can be used to create beautiful curves. The first step in creating a smooth curve in a sheet of cardboard is to make sure that the corrugation is running the right direction. The corrugation must be running perpendicular to the flow of the curve. Lets say you want to create a hollow cylinder, or a tube, using a sheet of cardboard. The ribs in the cardboard must be running vertically. Make cuts through only the first layer (the top flat linerboard), along the ridges in the corrugation. Make a cut in between every ridge. Once the entire sheet has been scored in this manner, the cardboard will bend to form a rounded shape very easily.