Obtain certification as a teacher of English as a Second Language (ESL) through a recognized program, either at a university or through an organization such as the Peace Corps. While anyone with a knowledge of English could theoretically teach it, the process of teaching a foreign language requires training and preparation.
Start by tutoring English to speakers already familiar with the language. Frequently, foreign students attending American universities will have a working knowledge of English but seek to improve their fluency in order to improve their grades and their job prospects, especially when studying scientifically rigorous fields where competition is fierce. By working with these students, you can gain experience in identifying common mistakes made by foreign speakers and practice methods of teaching English.
Develop a lesson plan. Over time, you will get a feel for how best to approach teaching English on your own based on a student's nationality and fluency. By developing a plan that starts with basic skills and moves all the way to an advanced level, you will have the tools and knowledge necessary to teach students at any level.
Build a client base through contacts, advertising and cold-calling. When you first start out, working with an agency that connects tutors to clients or through an educational institution, such as a high school or college, can help you make the connections you will need to get clients while building your experience and your resume. While you can work independently, you may be most successful if you work with an existing school or business that specializes in teaching English, as those with limited skills in the language are more likely to call a reputable organization rather than contact an unknown individual.
Learn from experience. As obvious as this seems, nearly everything you can learn about teaching English you learn on the job. Your experience with students will teach you what works and what does not while helping you to create a connection to your students, which is essential for a successful tutoring relationship.