If I had to share only one piece of advice to a new yoga teacher, it would be to read and study as much as possible immediately post teacher training graduation. Experiment with what style of yoga you enjoy to study and teach most. If the studying feels arduous, explore other specialties until the learning excites you.
As a new teacher, I was obsessed with the small details and nuance of a well-led yoga class like the pacing, clarity and deliberacy of cueing and in-class student support and connection. I would sit in the back of the yoga classes of some of my favorite teachers and simply take notes on what they said, how they said it and what its effect was.
My earliest journals are rich with examples of creative ways for putting language to concepts within the context of movement, alignment and philosophy. This form of self-led continued ed., paired with the readings from the books below are what I leaned on most as a new yoga teacher, finding them both to be incredible allies for giving structure to all that goes into teaching a great yoga class.