A quick anecdote:
My first lesson - and what a disaster! It was actually a cover lesson, so all I had to do was say hi (in English), and put a film on for the class to watch. Simple, right? Not quite as smooth as all that! First, all was well - we set it up, I pressed play, the laptop was working, the projector was projecting, the speakers were... speaking. Then it all went a little stir crazy. The projector decided it was too hot and turned itself off. The laptop decided it was too tired and went back to sleep. The speakers, thankfully, were still performing, but unfortunately, due to the tired laptop, they were beeping quite loudly every 5 seconds or so. And I had a class of about 30 students sitting in front of me, expecting me to do something about it! I took the situation in hand and decided that, instead of making myself look stupid and faffing about with overheated projectors and what like, I was going to do something I knew how to do - talk! In an English class, that's a pretty legit. way of passing the time. So, we had a nice chat about Uni life and UK pubs (apparently one o' clock is shockingly early for closing time). And then a very helpful student came back with a new projector and new laptop and very kindly fixed everything for me! Good times. Phew, first lesson managed! What an experience!