Through practicing, you will most likely discover that you already have many of the skills coaching requires. You may just need to focus on them more deeply, or use them in a new way.
Once you have some familiarity with questioning and listening, you may wish to try giving feedback. A good place to start with feedback is with yourself.
Think of a project you worked on, or maybe a specific task you completed. What kind of feedback could you give yourself, keeping in mind coaching principles?