Hindrances to Getting Hired as a Teacher Overseas

The economy has a lot to do with things. If there are no jobs at home, more people will be looking at going overseas. Don't think there's going to be a huge flood of teachers though. While numbers do increase when the economy goes belly-up, many people don't want to deal with moving and uprooting their families. You can read more at Laid-Off Public School Teachers May Flood the Fairs.

Keep in mind that some schools, such as international schools prefer single teachers or teaching couples with few or no dependents. If you are married to a non-teacher it may be harder to find a job. If you are married to a non-teacher and have dependent children it will be harder. There's a list of the best international school job fairs for people with kids and bringing dependents with you.

Age can be an issue as well. The cut off age seems to range between 55-65 depending on the school and the country that it's in. You might be too young as well. Malaysia, for example, won't issue teaching visas to those under the age of 26.

Not enough experience. Some schools prefer you to have at least 2 years teaching experience. Others may be willing to waive this requirement. 

Nationality can be a problem too. While many teachers want to teach in Europe, some schools don't want to jump through the hoops of getting work visas for those without EU passports or those who can already teach there (for example, spouses of EU citizens). Read Europe for non-EU passport holders for more info.

If you want to teach at an international school check out what esl4everever says on this post, "From what I understand American schools do not require you to have any type of dual or EU citizenship. American schools are backed by the United States Department of State. The schools are supposed to be ran by US standards to a point although they are located in another country." Whether this is true or not I'm not sure. It's best to check with each individual school. I know that DODEA schools only hire Americans or those with permission to work in the US, so that might be an option.

Not being certified may be an issue, though there are ways around it. Here's some info on how working as a PNET (Primary Native English Teacher) in Hong Kong could help land you an international school job.

Not being a native speaker. Some schools are very strict on this policy and will only hire native English speakers.

More information. There are also a number of good books that will tell you how to get an international school job.