Wood sometimes can shoot itself straight. I.e., little bends, not crooks, will sometimes come out over time through shooting. I don't worry about them too much in my practice arrows, but I always try to get my hunting arrows as straight as I can. Good advice already given on how to straighten. Keep in mind that you'll probably need to re straighten every once in a while, particularly with hardwoods. I carry my bow with bow quiver, under my arm when still hunting. Over time, the pressure of my arm on the center of the shafts in the bow quiver tends to put a slight bend in them. I check and straighten every few days under those conditions.