Good luck - no experiencing teaching but an ASD child.
The NAS has a guide if you haven't seen it already:
www.autism.org.uk/professionals/teachers/classroom.aspx
A lot of children with ASD are sensory so things like changing clothes can be stressful and noise/shouting can be difficult. He responds best to kind, calm but firm teachers.
Its often worth asking the parents - I've seen lots of teachers with DS and seen a lot of what teachers have done that works and a lot of what doesn't work. Don't necessarily need to follow what parent says but can give good insight into what works / doesn't and how is at home - mine is fine at home.
What has worked at school includes:
Advanced warning of timetables, lunch menu, PE activities and rules so nothing unexpected or a minimal amount.
Can be very reluctant to talk to teachers and discussing things he's comfortable with first can help relax him e.g. maths, obsessions then he will chat more but you may not have time for this.
No incentives to behave in an undesirable way so a quiet place/safe place to go but not one full of soft toys e.g. a library works. He does often need a quiet space and is best left alone.
Positive encouragement - DS had massive improvements in year 5 and teacher told him he was clever and sensible. He went from needing a full-time TA to none with her and that was largely down to her amazing ability with him and previous teacher ignoring Ed Psych.
When things have gone wrong its sometimes been partly as the teacher refuses to follow advice from Ed Psych and uses normal behavioural methods rather than ones aimed at ASD and shouting as they are often noise sensitive. It is hard for teachers though as he's in mainstream and think most of them have no or very minimal ASD training. There's little point trying to reason / have a conversation with an ASD child during a meltdown - ensure everyone is safe but wait until calm before having conversations. In conversations adding positives as well as negatives helps and depersonalising helps.
They can also often underperform in exams over natural ability - I had to teach my DS to ignore questions he couldn't do as at school he would just give up at first one couldn't do even when can get 90% right. English he will answer what he thinks the correct answer is not what the author thinks, he will generally be right scientifically but its not what he's being marked on. ASD kids can be perfectionists and doing well can be very important to them, maybe partly as less social success.
Limited diet and allergies / intolerance to food are common - separated food is often better. Food often needs to look identical though school dinners are good for that.
They are all different though but the NAS guide should have some common methods. Mine is allowed to leave class when he feels stressed and go to a safe place.