This varies by state, drastically. In NY state you need a masters degree within 5 years of teaching and a bachelor’s degree to start. There are also all sorts of other requirements like teacher certification exams, child abuse workshops, fingerprinting, 1 year of a foreign language, student observations/teaching, and misc. program requirements at each university. Getting certified in NYS is actually a tedious process. In general, you need to be knowledgeable, patient, flexible, reliable, and have a good personality to be a good teacher.