If you're going to teach trainee teachers or colleagues just one rule about technology, it should be this:
It's not a question of if the technology goes wrong, but when.
That's obvious to those of us who have been around a bit as far as education technology is concerned, but not to those who haven't. In my experience, when something goes wrong for a teacher who has decided to use some ed tech perhaps for the first time, they personalise it. They think it must be something to do with them, or that they are naturally incompetent.
In fact, when I was running some training for teachers a few years ago, two really good things happened.
First, something went wrong: the interactive whiteboard stopped interacting, thereby rendering useless my hours of preparation, and depriving the participants of a really good experience.
Why do I say that was good? Because several of the teachers there said they felt reassured by it: "If it can happen to an old hand like you, then we know if it happens to us it won't mean we're useless."
Secondly, after my initial two or three minutes of trying to get it to work and phoning for a technician, I resorted to plan B, which meant that the session still went ahead, and they still had a good experience. That was good because it exemplified good practice.
To summarise, the fundamental rules of using technology in teaching are as follows:
1. It's not a question of if the technology goes wrong, but when. Anything can go wrong, at any time. In the early 2000s there was a widespread internet worm that even brought down Microsoft if I remember correctly. (The Chief Education Officer called me into his office and said that the headteachers were complaining that because of my team of technicians, their schools didn't have internet access. I told him that if he believes that my technicians were responsible for the worldwide stoppage then they should be given a raise for being so highly skilled. But I digress.)
2. Always have a Plan B, even if that takes the form of printed copies of your presentation.
Of course, there may be times that the technology goes wrong, and it is their fault. I'm not suggesting a complete abrogation of responsibility. It's up to the teacher to make sure they know how to use the technology, and that everything is in place (eg the device charged up, the video is in the correct format, the wi-fi connection checked and so on). But sometimes things will happen beyond their control.
It's important to recognise, though, that if you have the misfortune to have an inspector in your classroom when things go wrong, you won't be able to use that as an excuse for the kids not learning anything. Hence rule number 3:
3. Move from stage 1 (something going wrong) to stage 2 (Plan B) with the minimum possible delay. That means, do not try to fix the issue yourself once you've spent a moment or two going through the usual procedures (eg checking everything is plugged in, rebooting the device). If you phone for technical support, don't suspend the lesson until they turn up.
The basic rule is: continue with the lesson as soon as possible. That's why knowing the near-certainty of something going wrong is so empowering: if you realise that there's nothing much you can do in the situation, then you can carry on without being completely discombobulated.