It is best to shred your personal documents before throwing them away. Recently I saw papers flying around on trash day. Looking down I saw a mortgage application and bank statements. This person’s entire financial history was flying around in the wind.
When purchasing a shredder it is best not to get the least expensive machine. Low end machines jam and the motor may burn out. A better machine will last for years. Do not overload the machine or shred for a long time without stopping. If the motor gets hot let it cool down. To lubricate: use spray lubricant and spray a piece of paper before shredding it.
Look for cross-cut shredders and try not to send stickers through as they clog the blades.