Although there may still some countries that will hire you without a teacher certification, it’s in your best interest to get certified anyway. Why? You will learn a lot from the course, you will have access to more job listings, you should get a better idea of what to expect at your future job, and finally, you probably don’t want to work for a company that is desperate to hire anyone regardless of her/his credentials.
There are many kinds of certifications and they differ in length of study, price and location. Courses can be completed online or in a classroom. Some jobs specifically require a ‘CELTA or equivalent’ certification. These courses are more challenging and expensive but are the most reputable. CELTA is the most sought after and is offered through Cambridge University. The next best is probably CertTESOL offered through Trinity College London, and the third is SIT TESOL.
If you’re not willing or able to fork out the extra dollars for the above mentioned courses, here is a solid database for international and online TEFL courses. Also, Groupon sometimes has deals on online courses. Warning: A TEFL equivalent is a minimum 100 hour in class course with a minimum of 6 hours of practicum. Not sure which one to choose? Read some reviews from other teachers!
However, if you already know where you want to teach then do a quick search for jobs there and see what certifications are required. It could save you a lot of time and money.