What kind of bamboo do you have? Most make good arrows. Most of my experience has been with our native bamboo, river cane.
What diameter for 55-60# spine
With cane, about 3/8" or so at the big end usually works well. Spine will vary depending on the species of bamboo and thickness of the walls of the bamboo shoot. Cut them a little bit bigger than you think you'll need, they shrink some in diameter as they dry. You can also control apparant spine by the length of the finished shafts.
How to make self nocks in them
I like to cut the nock ends of the shafts off about a half-inch behind a node and cut a self nock in just like you would with any other shaft. Making it behind a node isn't necessary, but it reinforces the nock. You can also plug the ends of the shaft with a hardwood dowel and cut or taper it like a solid shaft.
Best way to straighten
With heat. Gently heat the shaft until it starts to "sweat", at which point it bends easily. I like to straighten the areas between the nodes first, then do the nodes themselves. Other people do the opposite, whatever works best for you. Once straightened, bamboo shafts seem to stay straight better than wooden shafts.
How "green" should they be
A month or two of seasoning is usually enough, just depends on the conditions. Usually when they start to "yellow up", they're getting pretty well seasoned.
Do I need to seal them
Most bamboos have a shiny "rind", which is fairly waterproof. I often make cane arrows without sealing them at all, but it's not a bad idea to put a finish of some sort on them.
