I have processed driftwood twice for my tanks. I researched it thoroughly before proceeding. I first cut, chisled, debarked, and wire brushed the wood. It then boiled for an hour or two at a stretch, changed the water and then boiled again. I did this for two days.
It then went into a "soak tank" (20g aquarium) at 90 degrees for three months. I also had a halogen light installed in the hood to give the wood a bleached look. After the three months I put the wood in the aquarium and haven't had any leeching.
The site also said that if boiling wasn't possible, that it should soak for three years first (!)