Sharpen turning scrapers upside down on the bench grinder; the downward motion of the grind wheel creates more of a burr!
Make your jam chucks from a softer timber than the piece to be held. (courtesey of Jules Tattershall Jan 2004)
Don't fold your abrasive paper more than once; that way you can feel the build up of heat between abrasive and wood before it does any damage.
Alternate power sanding with hand sanding. The former produces more random scratch marks whilst the latter leaves circular marks. By alternating the two you can see when one your abrasive has completely removed the marks left by the previous, courser grit. (courtesey of Jules Tattershall Jan 2004)
Be wary of burnishing rough burrs and open timbers with paper tissue or shavings. The open grain can tend to capture small bit of shaving or paper and you're then faced with a long session with tweezers to get the bits out!