Something that I learned while going through early intervention with my son, is the PECS. It looks something like this. The blue part is stiff paper and the white part is Velcro. You print pictures of things that happen in church, such as: praying, talking with a microphone, singing, teaching a lesson, scriptures, etc. I also include getting a drink and going to the bathroom. It's best to have pictures of ANYTHING you may do in primary or class.
I use it as a picture schedule. You can either put the pictures on the bottom when it happens or take it off. It helps the kids understand better by seeing what is expected to happen. I use it for both the class and sharing time. One thing to remember, if something like this is used, it might be a good idea to sit in the back or to the side so the other kids don't see it and get distracted.
The next important thing to remember is to make statements instead of asking a lot of questions. There is less pressure on the child and they will be more relaxed around you if you make simple statements like "Wow! He is brave. Lions would scare me!"
If you do ask a question, make it simple and give them time to answer. If it takes a "typical" child 10-15 seconds to answer, allow 30 seconds for a child with Autism.
I'm truly amazed about how many caring primary workers/presidencies are out there now. As a parent, I know how much it makes a difference. I can't tell you how many families find it too difficult to attend church and just stop going for a time. My husband and I were in this category until we moved to our current home and found an amazing primary teacher that went out of her way to connect with Jackson.
Good luck to all you primary workers! I feel strongly that it's a calling that can change your life if you let it.