There are many. If we were to prioritise, here is the list:
Teaching in a way that makes people feel they had the best trainer
Make people learn long term
Making people feel they want to come back and be taught by you again and again
Mastery of the four corner stones of training
Knowing what to do at any given point in a course
Starting confidently and with ease
Learning how to facilitate a training course and keeping delegates constantly engaged
Improving your rating as a trainer and getting best feedback