Regarding qualifications, it depends where. As a rule, the higher paying countries (Saudi
, etc) are looking for more qualifications and a few years' experience as well whereas Egypt
is less strict and a degree + TEFL cert is fine in many cases.
Again, there are many differences in lifestyle and expectations depending on which country you go for. Respect for religion is higher in some places more than others, drinking of alcohol and freedom of expression also varies. It can be a rewarding place to teach but if you are thinking of making a long term experience then I would suggest you choose your country carefully!