You need dead wood (green one has sap that might cause problems), preferably ones that had aged a few years & free of bark. And if you can find one in the bottom of a stream or something, then you save yourself a lot of trouble sinking & leeching it.
I collected all my driftwood from a remote stream in BC. You want to go somewhere with NO farm runoff (risk of pesticides that can stay for years & kill your fish/plants).
Once you find a piece you like, you will need to clean it. Remove all loose stuff, rotting wood, etc. I use chisels, scrapers, wirebrush & pressure washer (no soap). Then you sterilize it. There are different ways .... Heat is the most common - boiling it for a few hours, heating in oven or BBQ, etc. Big pieces that don't fit into your pot, can be sterilized by soaking. You can soak it in brine, bleach, or Potassium permanganate. This gets rid of surface stuff, but can't get at stuff inside the wood. With all soaking methods, you will need to rinse very well. I also leave the washed/rinsed wood in the hot sun for several days to sunbake & to remove/break down any residual bleach.
Finally, you will need to waterlog the wood & leech out the tannins. Weight down the wood in a big barrel of water. Change the water every week or so, and soak until the wood sinks on its own & no more tannin comes out of the wood (ie your soak water is clear). This will take a few months. If you don't mind the tannin colour in your tank (it is harmless), you can weight down the wood in your tank instead. As said before, if you find pieces from the bottom of a pond or stream, it would already be waterlogged & mostly leeched of tannis so the soaking need will be minimal.
80 gal FW with 30 gal DIY wet/dry/sump.
9 fancy golds, 1 hillstream loaches, 1 rubber-lip pleco (C. thomasi), 3 SAEs, small school of white cloud minnows, planted.