Invest in a decent machine. Cross cut shredders are far better than the cheap ones that only cut the paper into strips. It is possible to piece the long strips back together. Just ask the people from the US Embassy in Iran almost thirty years ago. I would also invest in a shredder stout enough to handle credit cards and CDs/DVDs. Office supply stores offer lubricating sheets that you run through every once in awhile to keep it in good working order.