TEFL certification is required in many parts of the world. In Europe it is almost essential - especially for new teachers. Even where it is not necessary, having some form of qualification will give you a competitive advantage when looking for work. It can also make you a better teacher.
There are many types of TEFL qualifications, but the main form of initial qualification is the TEFL certificate There are also types of qualifications which are aimed at English teachers with more teaching experience, for example the TEFL diploma.
Having TEFL qualifications will not guarantee you a teaching job. No piece of paper can do that. However, it will mean that many language schools, that wouldn't otherwise have considered your application, will now consider you. It will allow you to apply to better schools, with better conditions and pay.
My first ESL job was in Taiwan, where I worked without any form of teaching qualification for 18 months. I then moved to Spain where a TEFL certificate was asked for by almost every school. I had a very limited choice of schools to work in. Arriving in January did make the situation worse.
I found work in a low quality school in central Madrid, where students and teachers often waited outside the school for the boss, who was often late, to come and unlock the doors. Not surprisingly, the school began to lose students. After I took the certificate I left this school, and was able to take a job in one of the best English schools in Madrid. My old school went out of business a few months later.
Whenever there is a recession in North America and Europe, a wave of English teachers sweeps around the world. During these times, the value of possessing some kind of tesol qualification increases a great deal. When language schools are free to pick the best qualified candidates for the job, they will. Many language schools in the Far East and South America are not bothered by lack of TESOL qualifications. However, even there, the possession of a TEFL certificate will give you an advantage with some schools.
Another reason for taking a qualification is that it will help make you a better teacher. Teaching English is a skill. Do not believe the people who say that being a native speaker is all that's needed. It's not true. I've observed hundreds of English teachers, and it's clear that being a native or fluent speaker of English is not enough by itself.
Learning how to plan a lesson, learning what kind of ESL activities are suitable for teaching children, or adults. What activities are best for teaching English pronunciation vocabulary, grammar, speaking, listening reading and writing What are good ESL conversation topics and how do you make them work. What about ESL stories, and when are ESL games suitable. A good TEFL certificate course will help prepare you for these kind of activities, and will also give you ideas on how to manage a class of learners. When teaching children for the first time, ideas on managing the class will make your experience very much better.
There are a great many kinds of TEFL certificates available. These range from online courses, combined online and residential courses, to a vast choice of residential TEFL certificate courses. The Big 3: the CELTA, the CertTESOL, and the SIT TESOL certificate are the most widely recognized TEFL certificates. And they are also the most expensive.
The standards vary a lot, and this is even true of the recognized Cambridge and Trinity courses. Most language schools look for about 100 hours of instruction, including about 6 hours of observed teaching practice.
Whether you want to spend more on an internationally recognized certificate course, or save money by doing an online course, probably depends on where you wish to teach. In most of Asia and South America, where most schools are not too concerned about TEFL qualifications, the cheaper alternative may do. The choice is yours...
The TEFL diploma is for teachers with a few years experience who want to take a further qualification. Again, the two most widely recognized diplomas are from Cambridge University (DELTA-Cambridge diploma in teaching English to adults) and Trinity College London (Dip TESOL-diploma in teaching English to speakers of other languages).
If you decide to make a career of TESOL you might consider taking an MA TESOL.This is only really necessary if you want to teach in a university, or if you wish to make a change of career, and go into research. Then doing an MA TESOL is a useful first step. An MA TESOL can also be useful to help you enter other areas of TESOL, such as teacher training, materials design, testing, ESP, or any of the other specialisms taught, but it's not a requirement for entering any of these fields. Many TESOL jobs in the Middle East require a master's, and if you want to earn the higher salaries in that part of the world, then taking a master's degree could be a good choice.
If you are interested in teaching in a university, a PhD TESOL or applied linguistics might be interesting. Increasingly it is becoming a requirement for university work around the world. Taking a PhD is a big commitment in time and money, but it will pay off if you really decide a university career is for you.
If this is the case you really have little choice but to take a PhD. This was not so true in the past, and there are still many English teachers working in universities with only a master's degree. However, as more people take MA's, PhD's become more valuable. The more popular universities are now able to require this.