Ideally, you would want to take a course from a reputable provider in the country you would be teaching at.
If not possible, you would want to take it in your area. I'd advice on an onsite course even if you're would-be employer would be fine with an online one. You'd be investing for the long run.

stuff that you would need:
work visa/permit, most of the time your employer will help you with that.
diploma, birth certificate might be needed as well.

a quick google search for recommended Ethiopia shots
http://www.mdtravelhealth.com/destinations/africa/ethiopia.php

I'd really like to suggest TEFL International if you have them in your area. I took one of their specialized courses and not only did their course prepare me but the certificate hasn't either.