I were teacher in two functions, but only in a wider sense, not an academic teacher. First it was meditation, and second combat trainer for security personell (which went terribly wrong).
From the first, this: the real important things to learn, people do not learn if you give it to them in advance, on a silver plate. Let them come to ask the right questions first. In other words, don'T teach in advance so much, but answer questions. It is important for a student to find the right questions first. You can form a library of blueprinted answers and prepared solutions when being given learning content on a silver plate, and memorising that - but that does not automatically mean you truly understand the matter, and any problem for which there is no solution in your memory has a good chance to throw you off your tracks. True understanding of a matter always is a systemic approach. By the way you answer the questions raised by your students by themselves, you can influence the focus of their attention on what you think is important for them, you can inspire their confidence and increase their competence. Do not mark the target for them. Let them discover the matter themselves.
From the second: I overestimated a trainees' capability, and accidently almost killed him, injured him very badly instead. Terrible experience for him, and for me as well. Lesson to be learned from that: do challenge your students, but do not overcharge them,
and do not take skills as granted - make sure they are there before basing on them. Else you at least waste your time, and the good preparation for the next lesson that you spend all night over, will be wasted.
I currently read a book by Monty Roberts, the guy with the horses,
From my hands to yours. I read it just for curiosity and interest, unfortunately I have nothing to do with horses. There he answered a question somebody asked him, the question was something like what he has learned from his work with horses, and he replied with "What I learned from horses is to be friendly with horses and humans alike".
For most situations that probably is good advise.
If you want to build a ship,
don't drum up the men to gather wood,
divide the work and give orders.
Instead, teach them to yearn for the vast and endless sea.
Antoine de Saint Exupéry
P.S.
I'm probably hopelessly idealistic there, but then, I lack the experience of having taught in an academic context. But I knew several teachers, and my diploma paper was on teachers' motivation (amongst others). The sister and the husband of a good girlfriend of mine, my grandfather, several people I had some contact with from university times, and a good friend of my mother all were teachers, or still are - and they all died of cancer and before their time, or were or are cursing about the sad reality in schools.
I thought I charge your idealistic immune system a bit before shooting you down with the sad truth about teaching!
