^^^This. Be careful weighing it down.
Personally, I either:
-Just let it float until it sinks (could be a long while)
-Use stainless steel screws to screw it to slate or some other rock so it sinks with no fear of a rock being moved and my driftwood flying to the top of the tank possibly breaking something
other than that, I first spray it off with a hose. Then scrub really well with a hard bristled brush. Then spray off with the hose again. Then I put it outside on a table or something so it's not sitting on the ground, and let it bake in the sun for a long time. Then typically spray it with the hose and scrub again before putting it in the tank.
And I agree with the statement that the heavier the wood the better when looking for it. I only get dry wood (not submerged in teh river). And this has worked well for me.