It's a tragedy that instructing is the most common and (notwithstanding what this article says) the easiest way to build hours to get to an airline career. There are a lot of people who will make good professional pilots who should not be teaching. Conversely, there are plenty of people who are great flight instructors, but would make terrible professional pilots.
It's a constant challenge to use just the right words to convey an intended meaning to your students. I once told a student to push the nose down to break a stall. We went from stall to zero-g pushover in half a second, which is fine, but not what I was trying to describe.
I'm not good about this, but writing down clearances is a really good habit. A rule of thumb for me, if ian instruction can't be fully executed within 30 seconds, it should be written down. E.g. "Cessna 1004E, descend and maintain 4500, turn right 220, proceed direct DOCAL when able." I can program that into the G1000 in less than 30 seconds and it's done. Consider, on the other hand, "Cessna 1004E, taxi runway 13 via Golf, Kilo, Zulu, hold short of Zulu." This is not going to be done in 30 seconds. Write it down before you start taxiing.