First this is just my list and it may not be someone else's. We have a saying, "if you have met one kid with Autism you have met one kid with Autism." That means no 2 are alike. So, when we say our son has Autism then you tell us how a kid your son goes to school with has Autism, that doesn't mean anything to us and we really don't know what to say after that but "ok". They have ever different health concerns and different abilities.
Next, there is no Scientist or doctor on the planet who knows what causes Autism so please don't tell us you know it is caused by genetics. As a family that has had 3 genetic test we know it isn't. We say in the Autism world that "genetics loads the gun but environment pulls the trigger". What causes it in one person may not be the thing that causes it in another.
Lastly, Autism family members are accidental activist so we have no problem answering questions about Autism and most of us don't mind talking about it at all. We are not ashamed of it so it is not rude to ask us questions because the more you know the more others will know and that is what awareness is all about.