With ASD, the most important thing I have found for myself is to keep motivated and have some kind of goal or target.
I took a trip up to Scotland recently which I popped the video into the "Introduction" part of the forum and uploaded some pics to the photography part just now.
Everyone is different *but* I can say sleep is so important so that one doesn't suffer "burn out" like I did on the way back and ended up with a panic attack driving solo after 3 hours sleep and 7.5 hours on the road.
Also, keep things relaxed - though targets might be good for some people. I found that I felt too pushed or compressed for time; but then the first part I was kind of assisting a professional photographer so it was tagging along with his project. Recalling as a child now we did have some day trips to places with my family and it was fine. I think it was because we were all together that I felt safe but at the same time I had people to talk to so my ADHD didn't get so erratic either.
It really does depend a lot on individuality though as ASD is a really broad spectrum and actually I am quite high in certain places but then not others which makes me fall through the cracks and no one would realize immediately that there was anything there.....
If like me you're child suffers from heightened anxiety then figuring out certain triggers and mitigating those will be a good start. I also suggest a dark room with very little sound to prevent "sensory overload" situations additionally.....
One of my biggest issues is that I struggle with hordes of people and over-population which is the theme for my little island and especially down here in the south east of England. Having so many people and cars around really does stress me out a lot and it is so important to try to keep from getting depressed too. Once things go off the deep end the anxiety goes through the roof and the brain just cries for help.... I guess my best metaphor here is Idaho! Somewhere on a trail away from anyone that my mind feels comfortable being in.
Environment basically is important.
If you have any directed questions or anything I will do my best to answer as I have seen and been around many people on the spectrum, some with other issues like learning and developmental problems and others with mental disabilities etc... so I have some experience in the field outside of myself ;-)