I just got some Birch bark that I plan to back a bow with. My question is how does it need to be prepared, how long to let it dry, which glue works best and how thin should it be. I am using it to dress up a bow not for structural integrity, though if I get some of that I will be happy too.

Tony, is this paper(canoe) birch you have?  I have used it as a covering over sinew and used TBIII to glue it down. You can peel off a single paper thin layer and use that or separate a few layers in one piece to use. I soaked it in warm water first to soften it a bit, glue it down like snake skins then wrapped it with strips on old bed sheet. Ace bandage works to wrap too.
  I don't think you have to dry it first. Just use it as it comes off the tree. You can use it with the white side out or the tan side out.

Pat. It is yellow birch but has almost same qualities as the paper birch. I was going to put it on thin with the outside facing out. i thnk it will look real good and give some camoflage to the bow as well. Will post picks of the finished bow.

Tony, Try that on a sample piece first. I'm not sure yellow birch has the same qualities as paper birch. After it is glued down, if it cracks the crack will probably go into the bow wood and you know where that will get you!

That I will do. I still have to see if the bow can be salvaged from its splinter so i have plenty of time.