A cantor is the singing teacher hired by a church, charged with leading the choir and teaching singing. He is or her role may differ from church to church; for instance, a Jewish cantor may be considered a spiritual leader of the community, while a cantor in a Christian church may simply lead the congregation in singing hymns. Different congregations and faiths will also have different requirements for becoming a cantor, the most strict of which expect you to go through schooling.
To become a cantor of a Jewish congregation, you will have to yourself be part of the Jewish faith. It will also be helpful to find a mentor; as with most professions and aspirations, the process is made easier if you have someone you can seek guidance from as you go through the process. Your mentor should be able and willing to help you reach your goal and, if possible, should also be a good resource as you try to network.
The next step to become a cantor would be to develop your musical skills. You should be comfortable not only with your voice, but also with playing the piano, music theory, and other musical concepts. Many people who are looking to become a cantor will have some formal musical training, often from a conservatory of music or one-on-one with a professional music teacher.
As you develop your own musical talents, you may want to explore various cantorial schools. Meet with the deans of several schools to discuss your aspirations to become a cantor and perhaps even perform for them. This meeting will give you a better understanding of what is expected of you and areas you may need to work on. If, after learning more about the various schools, you decide that you want to pursue professional cantorial training, select the ones you would like to attend and go through their application process.
Once you have been accepted, the steps to become a cantor are not much different than earning any other job or position. It's important for you to attend your classes and do your school work. You'll also need to continually develop your musical talent, as well as any teaching/conducting skills you gain.
You'll also want to consider gaining some beginner-level professional experience in both teaching and musical situations. Some congregations may give you the opportunity to contribute, or you can seek out some less-formal opportunities, like local community productions or camps. The diversity of your experiences will be beneficial.
Upon graduating from cantorial school, the job search begins. Contact various congregations and see what positions are available. Use people you know, your mentor, teachers, and others in order to network and find possible open positions to become a cantor.