My autistic child is the youngest of my three so I did have to learn to parent differently. I walked a line between being fair to my older two and accommodating and learning how DS3 needed life to be.
Firstly, we had to slow down. Other people have talked about this, but things that worked for my older two, such as getting home from scout camp one day and going off on family holiday the next, don’t work for DS3. He needs a decent break between the two to reset.
Secondly, adjust expectations. We are all quite musical and we joked when he was born that he was going to be our bass player. He’s not interested in learning an instrument. Equally, he finds a busy dinner table a bit much and I am happy for him to get down once he’s eaten. MIL and FIL did not do that with theirs, so they, and to a lesser extent, DH have had to learn to smile and lump it. I’m lucky in that all the grandparents adore him and are happy to learn. I have friends with less sympathetic parents.
Thirdly, I have had to expend a lot of time and money on pursuing diagnosis, not so much for autism, but in having him assessed for SPD, dyslexia and other things. Some of it has been a bit mad - we spent a year or so doing nightly exercises for retained reflexes, which I was dubious about but he enjoyed.
One of the top tips I learnt from a parenting course I did with a local autism charity was that for some autistic children, it really helps not to vary your phrasing - so for example, saying ‘can you put your shoes on?’ Followed by ‘why haven’t you put your shoes on?’ And then ‘put your shoes on! You’re going to make us late’ is giving the same information three different ways and the child will need to process each sentence to determine that. Saying, for example ‘put your shoes on, please’ theee times avoids that. Actually this tip helped everyone’s mornings.
i like Jessie Hewitson’s book How to Raise a Happy Autistic Child - good read!