What I do is pick up deadwood that i know has been lying around for a long time. The bark should be easy to pick off it. If the wood is still hard with no signs of rotting I give it a good wash, bake it in the oven for an hour or two, and then give it a good soak before using it.
The key is to make sure it is hard wood that won`t rot, and that the sap in it has all dried out.
Cheers, Dave.