When choosing a TEFL course, there are 4 things you need to think about.
How much time have I got to do my TEFL course?
TEFL courses vary both in terms of how many hours they take, and the overall time you're allowed to complete it. It's possible to do an intensive, one-month, full-time TEFL course, but it's very hard work! If you do a distance-learning course in your own time, you can take up to 18 months to complete it if you need to.
What kind of TEFL course do I want?
You can do a TEFL course online or in a classroom. Some courses include teaching practice in a classroom environment. If you are new to teaching, you might find this useful.
Do I need help getting a job after?
Some TEFL schools offer job placements, others have job-finding help. Some will even guarantee you a job if you pass.
What qualification will I get?
The two main internationally-recognised certificates are the Trinity CertTESOL and the Cambridge CELTA (which is geared towards teaching adults). However, you may find that the job you're applying for will require only the 'equivalent' of the CertTESOL or CELTA, which means that the certificate from your school will get you a job.