How do most people enter coaching?

Your passion and love for the game should be the first and formost qualification to get into coaching. Since you have this question, i believe that is already met. Now coming to the specifics of coaching, you need a good understanding of the game and should be a great communicator to succeed as a coach. Most people transition from a player to coach role during the end of their playing career although its not uncommon to find people directly getting into coaching roles. In UK, the FA has multiple levels of coaching certifications that you can start with and then gain experience either as coaches for school teams or as assistants to senior coaches for senior teams. A lot depends on your understanding of the game and how well you can connect to your players and motivate them. Another thing to keep in mind is networking with the right people who are directly associated with the game.