Step 1. Paper
Damp, curled, or previously used paper causes roughly half of all jams. Try a fresh ream from sealed packaging before you start disassembling the device.
Step 2. The Tray
Check the side guides: if they press the ream too tightly or, conversely, are too loose, the sheet feeds crooked. Don't load paper above the maximum-fill line.
Step 3. The Pickup Roller
A worn or grimy roller slips and pulls two sheets at once. Wipe it with a lint-free cloth and alcohol; if the rubber is glossy and hard, only replacement will help.
Step 4. Foreign Objects
Paper clips, remnants of previous jams, and bits of packaging film. Always pull a stuck sheet out in the direction of paper travel and slowly, otherwise a torn-off scrap will remain inside.
Step 5. The Fuser and Duplex Unit
If the sheet always creases in the same spot at the output, the fuser unit or duplex guides are likely worn. This calls for an engineer.
What Not to Do
Don't pull the sheet backward, against the print direction, and don't use sharp-edged tweezers — you'll scratch the drum or the fuser roller.