The CELTA (Certificate in Teaching English to Speakers of Other Languages) is one of the most widely-recognized certifications. It is accepted by most employers around the world, and it is administered by Cambridge University. CELTA training centers are located in several places, and certification is only available on-site, and it is not available through distance or online education.
The DELTA is a certification offered by Cambridge to teachers of English who want to pursue more advanced study of the topic.
Online English as a second language certification programs allow students the flexibility to learn from home and on their own time. The price tag is manageable for most students as well: usually around $300.
Talk to other English teachers who pursued their certification online. There is no one accreditation body for any English as a second language certification program. This is especially true for online education providers. Find out from other teachers what their experiences with specific companies were. Look for companies who have good communication with students and with those that offer video trainings to allow teachers to connect what they read about teaching with a classroom.
Conferences that take place over a few days are another option for pursuing your English teaching certification. You will get a chance to practice your teaching skills once or twice, get feedback from other students and teachers, and earn your certification in a short amount of time. Conference trainings take place around the country throughout the year. Many companies that offer online training courses also offer conference trainings.
Take at least a 40-hour training for any type of certification you pursue. This is the minimum many overseas employers will accept. A 100-hour or more course is preferable.
Certifications from Colleges
Community colleges and universities often offer certification courses as well. These are often a semester to a year in length, and they are more in-depth than other types of certification courses. Certifications from colleges are often more accepted at adult English as a second language programs in the United States than other types of certifications.
Master's degree programs are also available for those who want to learn more of the theory behind teaching English as a second language. These programs usually take about two years to complete, and you will likely need a Bachelor's degree to enroll in such as Master's course.
References and Resources
TESOL Directory of Degree and Certificate Programs
ESL Teachers Board: Discussion Forum
Dave's ESL Cafe: General Discussion Forum