I am not one to preach to people on how to treat your child that has autism. Therapy, bio-medical, medication, there is an argument for any way you choose. Just being a parent of a child with autism is very challenging! The one thing I am going to preach about, is the fact that your child is in there, ever present and taking in everything that is going on!
I was lucky to learn this early on when I changed Sierra's diet. She had came out of her fog and I was amazed on how much of the stuff I taught her she knew, and then some! What I want to get across to everyone is to keep your child engaged at all times. Even though they seem like they are not listening or taking in what is going on, just pretend like they are. They want to be a part of everything and to be normal, their body just doesn't let them.
Here is a video of a Carly that is severely autistic but found a way (with the dedication of her parents) to communicate at 11 years old. This gives a lot of insight to how they think and feel.