When my son was first diagnosed, the psychologist told us that the one thing he had seen make the biggest difference was how informed the parents became. His advice? Read, read and read. So, I went on-line and I read. For me, forums like this became my preferred source of information, soaking up first person individual stories and considering what they offered in the way of suggestions to our family. Other people prefer more clinical reading. I could spend hours writing out strategies that I find extremely important, but if I'm going to narrow it down to one piece of advice, I'll have to agree with the psychologist: read.
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Mom to an amazing young adult AS son, plus an also amazing non-AS daughter. Most likely part of the "Broader Autism Phenotype" (some traits).