I related to Hathaway's answer in that I occasionally observe my colleagues teach. So, to get better, I go to the classroom. Fortunately, my position as chairperson for a period of five years afforded me opportunities to see other people teach. I always picked up a trick or two: a new way of asking a question, a different way of using space in the classroom, a technique for engaging students, etc. We all know it's easy to get stuck in a rut. Watching other people do their thing helps us to get better at doing our thing. I'm not chairperson any longer (and I notice a corresponding decrease in headaches) but I still peep into classrooms occasionally and linger outside classroom doors. That's not as weird as it sounds. Hathaway goes to the theater, I go to the classroom. But I can't buy a ticket to the classroom, so I hang outside so as not to intrude. But I still get to see other people in action. In what ways do they present information? How do they talk with students? What do they do well? What could they do better? What were missed opportunities? There's so much to see and observe.
I taught my first class in the fall of 1998. All these years later, I know one thing: I don't have it all figured out when it comes to teaching. None of us do. We work at our craft, work at being our best, and strive for those beautiful moments when learning is in the air. It's hard to describe when the learning happens (and we know that it often "happens" outside the classroom) yet we've all had that "aha" moment when something good happened. Teaching, like acting, is an art. To get better requires constant work and practice.
So, how do you get better?