First you want to find a fallen tree branch or alternatively find a young tree, if you use a young tree you will need to let it season (leave for two weeks or until normal wood colour). Make sure your wood is strong enough, dig your thumb nail into the wood and if it leaves little or no indent the wood is of sufficent strength. However if there is a large indentation it is not strong enough and will snap. Your piece needs to about 40" long for an adult sized bokken, for a childs bokken i would recommend 20". Also check the bend of the wood, make sure it is not to flexible or again it will snap. For my basic Bokken i have chosen this branch, i chose it as it already has a slight curviture so that it is not necessary to bend the wood.
Step 2: Preperation
Now that we have base piece we can start to shape our bokken. First you need to shorten to the required length (40" or 20"), for this you will require some descrption of saw.
Step 3: Smoothing
You now need to smooth down your Bokken base, cut off any spouting branches. Plain your wood to remove all the bark, try not to leave any deep cuts in the wood as these are often very visable. After that sand down your wood inorder to have a smooth clean blade and handle. I would recommend that you take the time to give a smooth clean finish.