What do you need to shred? Most paper shredders are adequate for basic paper-shredding needs. Those who will want to shred things like unopened envelopes of junk mail, multi-page documents fastened with staples or paper clips or data backup discs (CDs or DVDs), however, will need to look for a heavy-duty shredder that can destroy more than just paper.
Choose an adequate duty cycle. About 100 passes can be handled in five minutes of continuous shredding. Consider the cool-down time too: 20 to 30 minutes is reasonable, but some shredders require 90 minutes.
Consider a shredder's security level. Paper shredder specifications often include a security level based on the DIN 32757 standards (established by the Deutsches Institut für Normung or, in English, the German Institute for Standardization), and by the U.S. federal government. Ratings used in the United States range from 1 to 6, with 6 being the most secure and generally used for top-secret classified documents. For homes and small offices, experts such as technology writer Sam Grobart of The New York Times recommend Level 3 crosscut paper shredders.
Crosscut shredders provide more security than strip cutters. Most reviewers recommend crosscut shredders, which cut the strips into short lengths (those that cut the smallest pieces are sometimes called confetti-cut shredders), for shredding sensitive documents. Crosscut paper shredders that shred paper into pieces no larger than 4 mm wide by 50 mm long (the shorter the better) -- or approximately 0.175 inches wide by 2 inches long -- typically earn a Level 3 security rating.
Micro-cut shredders render the documents into tinier diamond-shaped bits, adding more security, though the extra cutting slows the shredding process. Strip-cut shredders slice documents into long, narrow strips. Unless the strips are very narrow, experts say it's fairly easy to reassemble them into the original document. That makes strip shredders only suitable for shredding documents without sensitive personal data.
Safety features are important. Paper shredders are subject only to voluntary safety standards, and some paper shredders lack features designed to prevent accidental activation or fingers being pulled into the blades. The good news is that most shredders include at least some features to prevent accidents. These can include slim paper intake slots, switches hidden in the back (to prevent turning it on accidentally), lock-out keys and blade guards.