The most common are image problems such as light, uneven or blank copies. If you have one of these problems, run a copy, turn that paper over and run it again right away on the other side. If the copy is better the second time, it's the paper. Press or lower roller may be out of place. On Toshiba copiers there are white caps on the front and back of the fuser section that may fall off and cause uneven pressure.
Paper jams are one of the most common and annoying things that can happen to a copier.
The most important thing that will help your copier feed is good quality paper. Paper comes in a wide variety of quality and if you buy cheap paper you get cheap paper. Cheap paper has an inferior grain pattern and feels slippery to the touch. Cheap paper curls more because of the way the grain lays, causing it to hit parts of the machine and jam. So, let's suppose you are the one that will be buying the paper.