I started teaching three years ago, without any formal training or even advice, on the frankly bizarre assumption that if you're doing a PhD you must be able to teach seminars. That means teaching things I know nothing about, at times - Nietzsche, International Relations, the history of car bombs. But it's fun, actually, and I think I have some ability for the performative and empathetic aspects of teaching even if I constantly feel ignorant or under-prepared. And colleagues in similar boats were incredibly helpful when I started.
This term I'm teaching much larger groups, of rich Americans rather than mostly working-class English people, about WW1. That will be initially quite troubling, I have never studied WW1 and I'll need to use a slightly different demeanour with the Yankees. But nobody can die, as my paramedic friend reminds me, at least not directly because of my actions.