Normally questions concerning material solicitation are shut down, but I think in this case, since it applies to orchestration, which is musical practice related to composition pedagogy, it is pertinent to this forum.
First, there are two great texts concerning orchestration: Alfred Blatter's "Orchestration" and Samuel Adler's "The Study of Orchestration." Adler's comes with a CD and DVD so you can listen to scoring techniques and see performers playing the instruments. Both texts contain registral characteristics within each chapter for each individual instrument. Blatter's text also include dynamic curves as well, which is extraordinarily helpful.
That said, there is no substitute for getting the sound in your ears and for talking with real musicians. Some musicians I have talked to disagree or laugh at some of Adler's registral descriptions. One of the wonderful things about orchestration is that it is equal parts technique and personal aesthetic.
So, books are helpful, but asking friends to play through sketches is exponentially more beneficial for the composer / orchestrator.