[I'm With Stupid]

CELTA or Trinity Certificate and nothing else. They're the most widely accepted courses in the world and are basically the bottom line in teaching English.

If you're only planning on working in a particular country, then you might be able to get by with a locally-run course that is widely accepted locally. But don't bother with any course that doesn't offer practical teaching experience with it, and don't accept anything with under 100-hours of study, because most employers won't. But to be honest, any less well known course worth the paper it's written on will cost about the same as a CELTA or Trinity certificate anyway.