It is not completely clear that it is possible to become a better leader. Leadership may be something that is simply innate and not learned. However, if one is to learn to be a better leader, there are two or three things (depending on how you look at it) that need to be done.
First, you need to lead to become a better leader. There is no substitute for practice. Leadership cannot be learned from textbooks alone.
Second, you cannot just practice. Instead, you have to practice thoughtfully. In other words, as you perform leadership functions, you need to constantly be analyzing how you have done. You need to look at things that have gone well and things that have not. You need to analyze them to see what lessons you can learn about your leadership. Just going through the motions is not a way to learn leadership. You have to put a lot of thought into it as well.
Finally, in order to know what to think, it is important to know about theories of leadership. People who study leadership say that there are various styles of leadership. It is important to know about these styles so that you can have templates to think about when you are trying to analyze your actions. You can then think to yourself: “which style was I using in that situation? Was it the right style for that occasion? Did I carry out that style of leadership properly?” In short, you have to have some sort of guide to inform your thinking as you analyze the ways in which you have performed as a leader.