Feeding in more paper than the recommended capacity can cause jamming and damage to the shredder. Keep this in mind when shredding folded papers or heavier paper types such as cardstock or file folders.
An overfilled wastebasket may interfere with the shredder's output, and can even cause already shredded paper to be drawn back into the shredder, causing it to jam.
If you intend to have your shredder on the floor, look for one with a simple vertical mouth that will be best for feeding the paper in. If you plan to place the shredder on your desk, an angled mouth is better.