Before you start on your journey fighting for the rights of a special needs child, you must understand what the laws are and what your child is entitled to. Knowing this will give you the foundation to build your case on.
Also, you want to get as much medical evidence of need as you possibly can. You'll be suprised on how many agencies will try to deny you based on "not medically needy". If you have documentation such as evaluations, therapy notes, doctor's recommendation, you should have all the evidence you need to present your case.
Hope that this answers your question. If you have any further questions, please feel free to ask. I've been advocating for my son for nearly 8 1/2 years,