The thing which helped with my son was all scaffold, scaffold, scaffold. In practice, this means anticipating things and planning all the time. Because waiting until you get to the event and then saying 'do x', it aint gonna happen. And telling him off 'after' he's done something bad - no way hosay, doesn't work, makes him crazy, I need to prevent him from doing the bad thing in the first place. It's hard to break it down because it's a million interactions every day we've learned how to manage in a way that often feels counterintuitive. The first time a psychiatrist explained what life would need to look like I thought they were insane.
I think a lot is making sure there are no surprises. Because a surprise equals a demand equals lack of choice and autonomy.
Examples:
Every night we sit down and plan what he'll eat the next day. He's involved in choosing and prepping food. If I plonk a plate of food in front of him it's a 'demand' and there's always a melt down.
Getting dressed is usually I dress him whilst he's floppy in bed (I know this sounds crazy but it works). If I told him to get dressed he would never ever do it and if I tried to make him he'd go bonkers.
Going anywhere we plan it in detail before, who will go where, when he'll hold my hand, what form of transport, what we'll stop and look at. So when we go to do the thing he's following a joint plan and there are no demands as he's following the script we've decided.
A lot of this is outlined (although terms like PDA are not used) in the book the explosive child which is helpful.
I just give the above as examples. But yes, if for example we went for an unplanned trip to the shop, he'd want to be super controlling (because he'd be anxious) which would result in more and more unreasonable demands, to stop, or go a different way, or buy something insane, with an inevitable melt-down when I'd have to say no.
Most of his friends are also autistic and they all tend to plan their games, who will say what, or play what, etc in advance (it's funny watching them!) as they all tend to like very controlled play. Funnily none of them like games of chance like board games where it's unpredictable who will win or lose. I tend to keep him away from kids who don't want to play like this as it just ends up in fights.