1. First, but a potty chair and a pull-up of course. If the child doesn’t feel like to do it, let it go. Try again after one or two weeks. Don’t make him sit on the toilet more than 10 minutes every time, once the child is getting tired, he will lose the interest of the potty or toilet.
2. Keep a record of the times and period the child gets wet and put him on the toilet at those times. Get him used to a regular schedule, for example, bring him to the bathroom every half an hour. Repetition and constant routine work for autistic children usually.
3. Make the child drink a lot(water or preferred drink). at every meal, so after about 30 minutes, the child would feel the need to elimination, put him on the potty then.
4. Parents could be a model for autistic kids. Let him watch the process you sitting on the toilet or potty and let him flush it.
5. Draw a picture of the potty or toilet and show him when you go to the toilet or when you take him to it. Or you can draw pictures of all the steps of going to the bathroom because children with autism are nonverbal.
6. Make sure the child sitting comfortable on the toilet while pooping, give him one or two his favorite toys.
7. Make it fun and interesting, like throwing a cheerio in the toilet which he can aim at.
8. After it, give the child some kind of reward if he goes or even tries.
9. Be patient. It might take a really long time before the child can go to bathroom himself, sometime, it could be years.
10. Email this behavioral specialist Maria: MBIRDWEST@aol.com. She’s wrote a book on potty training toddlers with Autism and she’s very nice.
Hope this helpful. Good luck!