First of all you need to know what type of wood it is.Most softwoods like pine are unsuitable.
Oak, beech,hawthorns and fruit tree branches like apple are some that can be used.Most hardwood trees are OK to use.
Make sure the branch is completely dead.This can take quite some time.It should feel very hard and rigid with little flex or bend.
It should not be green inside when snapped.It should be free from any sap.
All I do is wash the branch and poor boiling water over it and it's ready.
I tend to remove all the bark before I clean and boil the branch,it's OK to leave it on small pieces though.
Not sure if you have seen the tank below but this is all wood I collected.
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