In my experience of having been a student and a teacher in different capacities, the educators that have left the deepest impression on me demonstrate flexibility, humility, and personality. These three aspects embody that effectiveness in an educator is diverse and complex.
I chose flexibility because in teaching, as in life, things do not always go as planned. Neither students or teachers enter a classroom as a blank slate. Home, social, school, career are all spheres of life that we bring with us into any environment and understandably can derail an otherwise perfectly planned day. Whether it is rolling with the punches, modifying an activity or completely restructuring a lesson a flexible educator can more confidently face the unpredictable.
For humility, an effective educator is teachable, someone willing to struggle as a student. Teachers that I have had who admit to their mistakes and take responsibility for them become teachers that I respect. This is because they show me how to handle failure or hardship or just not being perfect. Humility is not constantly making mistakes on purpose but demonstrating grace in a sometimes unforgiving academic or behavioral environment.
Finally, an effective educator has personality. They have quirks and interests and hobbies and a unique way of seeing the world. I appreciate those educators in my life that shared their own passions with me. I still may not love math, but I learned to respect someone that does. Teachers that I have gotten to know become mentors and friends.