To understand others you first have to understand yourself. I often say that a mirror is an important tool - so that you can reflect on the impact that you are having , and what areas that you need to build and develop.
Self awareness is a key skill in both personal and work life. One thing that I have learned over the years is often the very thing that annoys you in others is something that you are not good at....if you are annoyed by the way that others are acting ask yourself why, ask yourself is it because it reminds you of something about yourself?
Being honest with yourself is so important.