well after the initial treatment before you add it to the tank, you don't really need to clean the wood. check out ebay and craigslist as well as the classifieds on here. stay away from using any pine, cedar, and anything still green. these will leech toxins into the water. grapewood should be avoided as well since it rots quickly and leeches tannins, a chemical that will both lower the ph and make the water look tea colored. hard woods like oak are desirable. you want a piece that is not rotting, has aged and dried out, and hard wood also tends to sink without much effort. boiling is recommended and will help get tannins out fast.