I've used boiling water to make beach drift wood safe.
The first thing you want to do is soak the in clean fresh water for about a week. This will help eliminate salts, organisims, tanins and any other junk in the wood. When soaking, change the water everyday! I soak my wood in large tubs outside. I just dump the old water out and fill new with my hose. It also helps to do it in full sun. I've noticed the tanins leach out quicker in the warmth of the sun. After this huge step is completed, then start your boiling. If the wood is to large for a pot (which most are), just stick the ends in the boiling water for a couple of minutes. Then (BE VERY CAREFUL WITH THIS STEP!!!!) take the boiling water and wood outdoors and slowly pour the water all over the wood. You may want to boil a second pot and do the same to the back side. Make sure to let the wood cool and dry before using.
Goodluck!