I generally go with boiling for 15 minutes. Also, another idea is to pour a whole small bottle of Hydrogen Peroxide 3% into a bucket of warm water, soak the driftwood in it for 15-20 minutes, then take out, rinse off, and do a quick boil. The HP will also kill off any organisms as well as algae. Don't need to get the large bottle of HP, one of the small bottles is more than enough. And the driftwood will bubble like mad as it's soaking.
Also to note, for those who don't know, the Hydrogen Peroxide will just turn to water within 15-20 minutes anyways, so you don't need to do a thorough rinsing. Just enough to get some of the crud off the driftwood, then give it a quick 5 min boil. And if it sinks, you don't even need to boil it after the HP treatment, just rinse and go straight to the tank.