Whether its your own child or whether you are working professionally with neuro-difference, the most important thing is to avoid the Cell Danger Response.
Kids with neurological difference often have over developed amygdalas, producing too much stress hormone (cortisol). Bad sensory triggers often set this neurological artillery off - what we call meltdowns. but even if the kid doesn't obviously melt down, they can shut down, go inside, at the drop of a hat, if the wrong sensory trigger is present.
To understand this, start with yourself. What do you love sensorily? Sunshine? Warm water? Music? Silence? Then ask yourself what do you hate? Fingers on a blackboard? Flickering fluorescent lights? Loud industrial noise or certain smells? Conflicting noises - TV and radio on at the same time?
If a good sensory trigger is present when you're trying to learn or connect you will have a better chance of success than if the ones you hate are present.
Now imagine that effect - especially the negative effect - magnified 100 fold. Trying to teach or learn something in that situation isn't likely to be very successful. In fact it could be harmful because too much cortisol is toxic for the body and scars the brain.
Fortunately, the brain also regenerates itself very very fast (neuro-plasticity). So changing the environment to get away from the bad sensory triggers and introducing good ones that you know the child likes can retrieve the situation and repair the damage astonishingly fast.
So find out what your kid loves and what he/she hates. Find it out for the kids you're going to work with. How can you do this if they are non verbal? Observation - where do they always go, what environment do they always seek out? What shuts them down and freaks them out? And consult with the experts - parents and more especially siblings who know their brother or sister way better than anyone else.
This sensory information is the key. Use it and you might just unlock the door to Narnia.