How to Be a Better Teacher in a School

When teachers are within a school, they're often SLT ordering kind of external CPD and so on. And it always frustrates me a little bit because there's often real good expertise within the school itself. It's often the case that teachers just don't get chance to go in in each other's rooms and learn from each other. So I guess my question is, if you're a teacher in a school wanting to learn from colleagues how to get better in terms of behavior, how do you go about that? Is it worth watching more experienced teachers or not?