I've been looking to do the homemade driftwood thing myself and been hunting around for methods to do it. I have yet to do any of it myself, but plan to start soon. Everything included here is just stuff I've read. Here are a few things I've read about.
Wood has tannins. Tannins naturally reduce your PH. If you have hard water adding a piece of driftwood will help reduce the PH. This is good if you have fish that require soft water.
Get hard wood. Soft wood, unless you do an awesome job of sealing it in a fish safe silicone, will rot. If you can make dents in the wood with a finger nail the wood is probably too soft.
Get clean wood. Don't use pine. The stuff that leaches out of pine if you sink it is called turpentine. You don't want to be dosing your fish with turpentine. Don't use aromatic wood. The stuff that makes the wood smell good with leach out into your tank and potentially poison your tank. I do not know which woods are safe for use. I really wish there was a list out there. If someone has a list of good wood out there I'd love to see it.
Clean your wood. Using a hard brush, brush everything off it, including the bark. Bark has a tendency to rot quickly and pollute your tank.
Bleach your wood. No, not with bleach. Boil it with lemon juice of vinegar. Boiling it this way should get most of the bad stuff out. If you have pieces that are too big to boil I've heard of people using their dishwasher (without the dish washing detergent) to bleach their wood. From here, you want to try and remove a good chunk of the bleaching agent. Boil your wood in a chlorinating solution the same way you bleached it.
Leach out your tannins. If your intent is to naturally reduce the PH and hardness of your tank then you're good to go. Ignore this step as long as you don't mind discoloration. One method is to continue boiling the wood for as long as it takes to stop leaking tannins. The other method requires a few weeks. Soak your wood in hot water until the water discolors. Repeat until the water doesn't change color and the PH stays close to constant.
Sink your wood. Initially your wood may or may not sink, depending on hardness and how wet the wood was to begin with. If your wood floats and you can't wait to get it in your tank you can anchor it with fishing line tied to a rock until it sinks on its own. Alternatively, you can use some fish-safe silicone to glue it in place. If you have the patience of a saint you can keep it in the tub you were using to leach tannins until it sinks on its own, or, again, keep boiling it until it sinks or you have wood soup (just joking on the soup).
I hope this helps.
Remember, this is just a collection of information I found while surfing the web. Some of this could be wrong, or slightly incorrect. If it is please speak up.
