'As a teacher coach your job is not just to get teachers to change behaviours but to promote changes that will have meaningful impact on student learning'.
This is one of the biggest time and effort wasters I think I've experienced both as a teacher and in supporting other teachers. If you don't focus on things that really impact student learning, then what is the point? You put in a lot of work for little results because you're not making tha changes that are most effective in terms of student learning. But sometimes that can be really tough. Teaching (not to mention learning) is a really complex activity. Knowing which areas to focus on, in what combination and at what time is one of the hardest things to get right.