Before I signed up for an English teaching certification class, I spent 50+ hours reading about all my options. Maybe it is because it was the first big step in moving to Thailand, but also because I wanted to get the most for my money and time.
I imagine that, for everyone, it is a balance of cost and practicality; what you want to get out of the course and how much you're able and willing to spend.
For me, I liked the flexibility of teaching anywhere in the world and I didn't go to a big name university, so I thought the solid reputation of the CELTA was appealing. I wanted a challenge that would thoroughly prepare me for teaching abroad and I figured Cambridge's reputation was good for a reason. I also found that most of the reputable courses exceeded $1,300, so I figured it was only a few hundred dollars more.
Thailand is also one of the cheapest places to do a TEFL course, including the CELTA. For teaching in Thailand, there were many TEFL course providers that ran the CELTA a close second (some were spread over a 6 weeks, which is ideal if you have the time - it's a lot to cram into 4 weeks, but for visa and housing reasons, 28 days was more accessible for me)
I decided to take the CELTA and I was very happy with that decision. Here's why:
It exposed me to a lot of classroom time, observing my peers and the instructors 4 days a week for 2-3 hours, and teaching myself (eight 45 minute classes-2 each week).
It pushed me to my limits, forcing me to prove myself. This made the course very rewarding, especially by the end, because you have to give it your all and you don't doubt for a minute that you earned the certificate. Its a big confidence boost and reality check at the same time, especially for those with no experience.
The instructors were top-notch, diverse, and dedicated. They came from a variety of backgrounds and expertise, but they all had many years of experience. It was great to see the benefits of different teaching styles and to have different personality types. Every course had 2 instructors and there were also videos of other instructors in their library that you could watch.
Taking the course in the country, and ideally the city, where you want to teach means instant connections to jobs and a group of friends that is likely to include some others who will be staying in the area after the course is over.
The school is relatively large. Even though classes are around 16 people, there are multiple courses running in the same building, so there's a good chance you will meet someone you really connect with.
The course attracts a variety of people, from nationality and experience level, to personality type and age. They also do a good job of mixing the groups so you get a little bit of everything in your core group of 6.
When looking at courses, I recommend considering a few things about yourself as a student.
Do you want to teach in more than one country with your certificate?
Are you willing and able to work under a high pressure environment for 4 weeks?
Are you willing to give and receive feedback about your performance with your peers?
Are you looking to genuinely improve your teaching?
If you answered yes to all of these questions and you can afford a CELTA program, I would highly recommend it, ideally in the place where you want to teach unless you already have good job prospects.
Now, once you've settled on a course, this is what I would recommend for getting through it with your sanity and self-confidence:
Get sleep. It will never be enough, but the more sleep the better. You'll handle unplanned changes better, you'll be nicer to the people around you, and you won't burn out as quickly.
Do some recreational reading before the course. If you are really interested in being the best teacher possible, pick up some reading before hand. Try to familiarize yourself with some teaching games or online resources that might be useful. The more you know from a book before the course, the better equipped you'll be to exploit the expertise of your instructors for information that isn't as easy to find. You'll ask better questions, the lessons won't be over your head and you'll be less stressed.
Take time to relax on the weekends doing whatever helps you manage stress; exercise, time in nature, exploring a new part of town or having some drinks with friends.
Work hard and don't look back with regrets. You'll still learn a lot and make plenty of mistakes but the harder you work, the more you'll get out of it (while this makes sense to me, I was amazed at the number of people who didn't seem to understand this).
Accept your weaknesses and embrace your strengths. These courses can make you feel very insecure about your skills because you are constantly being scrutinized, but no teacher is perfect. Take time during the course (though the self-evaluations sort of force this on you anyhow) to think about your strengths and exploit them in your teaching.
Look for ways to balance your weaknesses with your strengths. For example, I found I excelled at lesson planning and forseeing problems with a lesson but I wasn't great at on-the-spot problem solving with a classroom of people and tended to panic. For me, I exploited my lesson planning and always had backup worksheets for students that struggled or were far ahead and backup activities if the students weren't engaging in a particular activity.
Take time to plan and try new things, but also take time to write things down that went well or didn't and why immediately after your lesson. These notes will be invaluable later that day, the next week and even the next year as you develop in your teaching career.
Don't be afraid to take risks. It is a good idea to run it by an instructor if it is really out there, but most risks will prove to be an unbelievably valuable learning experience.
I wish you the best of luck on whatever course or career path you take. Please let me now if there is anything I can add or expand on.