I used several large pieces of driftwood from a lake in Kansas. They were all dry when I found them. They worked great!
The rule of thumb is any wood that you can dig into with your fingernail is too soft. It will break apart in your tank within a year or so. Any bark will fall off, so scrub all the bark off (if there is any)
I didn't boil my pieces, they were large pieces, and I didn't have a pot or barrel large enough to boil them. I upped my hot water heater to its highest setting and sprayed all the pieces down thoroughly in the shower.
I then submerged them in water with some bleach mixed in for 30 days.
Then I put them in my (brand new) tank. They were still quite buoyant. It takes like 6 months of being submerged for larger driftwood to sink on its own. I siliconed my driftwood to the tank. You can try attaching the wood to large rocks or slate, but it may take a lot of weight to get the piece to stay submerged.
I noticed considerable tannins coming off the wood for about 6 months. The water turned noticeably brown within a few days of a large water change. After around 6 months it wasn't noticeable. Supposedly if you boil the driftwood thoroughly it won't release tannins, but I think it still would, just less.
Overall I highly recommend getting and using your own driftwood. Large pieces are VERY expensive, and if you're willing to put forth some effort you can get some awesome driftwood yourself.
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