Firstly, it is hugely, hugely dependent on where in the world you want to teach. You will be able to find a job in some countries without a degree, and even without a TEFL certification, though as you might imagine these jobs aren't likely to be particularly alluring. 

The majority of Asia requires you to have a degree in any subject, though something English based is beneficial. That's it. Korea, for example, has a huge ESL industry and the ongoing - and unfortunately quite accurate - joke is that anyone from one of 5 eligible English speaking countries can work there as long as they have opposable thumbs. The kind of job you can land will vary, however, depending on experience and further qualifications. Public schools and private language institutes are the most common, a university teaching job usually (though not always) requiring an MA in anything. In Korea the MOE or private employer will provide you with your airfare and accomodation,  which when combined with the low cost of living enables people to save a substantial amount of money per year if they try.

Japan is different, of course. Being JAPAN, it's far more popular and therefore the benefits aren't as good. Again, you only need a degree to land a job there. However, whilst you will get paid about the same amount as Korea, the cost of living in astronomically higher and you'll have to pay for your own rent and airfares in the vast majority of cases. Universities in Japan typically require a Masters degree and 3 published articles. Much, much harder to get than in Korea.

I think you're able to get a Visa in China without a degree, though more and more employers are looking for more educated employees. The cost of living is low, but your wages will almost certainly be a lot lower than in Japan or Korea. I'm not sure about their views on CELTA and other TEFL certifications, but most places in Asia don't really recognize these.

Looking at Europe, or South America, or Africa, a CELTA or CERTESOL becomes much more important. These courses, which can be intensively completed in a month (costing about 1000-1300 pounds, depending on where you take them), are pretty much required in much of Europe. There are numerous other cheap TEFL options too, some online, which can cost anything up from 50 - Experiences will vary.

If you have a Masters degree in Applied Linguistics, Education, or perhaps even English, your options open up further. University jobs around the globe will be open to you, though finding good ones is easier said than done. 

Lastly, if you have QTS (from a PGCE, for example) you can work in International Schools. The pay in these is, typically, better than an unqualified teacher will be paid. You can find these schools pretty much anywhere in the world - I was reading about a pretty interesting one in Tokyo earlier today - and they are one of the better ESL jobs alongside university teaching.

As for your final question, I think it depends on you. The vast majority will go home for whatever reason, usually after 2 or 3 years or working abroad, and a lot of folk think it's a road to nowhere. I disagree with this, though in Asia employers will start blanking you once you hit 35. Some people have without doubt done ESL as a career. It's very much what you make of it, I think, and working abroad can open up a wealth of opportunities.

@Tiger
I keep my eye on a couple of Asia news blog sites and I am starting to notice a real (no other word for it really) racist tendency creeping into the media in countries like Korea and China.
To put no too finer point on it, the main news channels (especially in Korea) have been running blatantly racist anti foreigner articles lately that are a little concerning.
Articles about teachers and articles about how cheap women are who go out with foreign men.

I have also read a couple of articles about white people being mobbed in China, usually followed by comments calling for the expulsion of the white, hairy, morally degenerate barbarians from the country.

As you have been or where in Seoul for a while have you noticed a shift in attitudes?

There is definitely a lot of covert racism in Korea, which bubbles over in particular news outlets (MBC being one in particular).

I think attitudes are actually improving in general, but the people running said media and much of the country are still very much behind the times. It's important to remember in this instance how recently it is foreigners actually started living in Korea (only the last 60 years or so) and how it is only very recently the country was heavily subjugated and their culture nearly wiped out. The result is a nation proud of their heritage and culture to (beyond) a fault. Over the past decade the ESL industry in Korea has boomed due, partially, to one-upmanship with Japan (having a population largely able to communicate internationally is desirable for the powers that be) but the measures in place to stop sleazy morons moving here are inadequate. Combined with the large US military presence, there are a lot of people who give foreigners a bad name in Korea. Also, I think there's concern about the westernization of Korea, which, I suppose, leads to women being more liberal than they were previously.

You do get older people staring at you, but the racist tendencies that irritate the most are the people who are so unbelievably fucking ignorant of anything but Korea and assume the rest of the world is full of imbeciles. A former co-worker once asked me if I could count Korean money.

Oh, and the majority of Koreans believe if you leave a fan on in the same room as you while you sleep, it will suck all the oxygen out of the room and kill you. Seriously.

Tempy - Get an MA in Applied Linguistics, move to Saudi. Get money.

Oh, and the majority of Koreans believe if you leave a fan on in the same room as you while you sleep, it will suck all the oxygen out of the room and kill you. Seriously.

This is it. This is how they'll get Kim Jong-un.

Supposing his dolly bird isn't a CIA murderbot already.

Yo if you want some overt racism head on over to Singapore.

To paraphrase a story from my bro who works and lives out there as a civil engineer and had the following conversation:

Native co-worker: "Roujin's brother, do black people and white people get married in the UK?"
Roujin's brother: "Umm, yes."
Native co-worker: Wow! So do asian people ever marry black people in the UK?"
Roujin's brother: "Yes, everyone can marry anyone they like."
Native co-worker "Haha, wow. That would never happen over here."

I was in Malaysia last year, up north in a quiet village for a friends wedding.
In the street I barely got a glance, which I found very odd as I was literally the only whitey in the village, but when we went to the actual wedding reception, complete strangers where queuing up asking me for photographs with them (I am not the slightest bit photogenic), one girl at another meal very shyly asked me if she could stroke my arm! She was fascinated by the fair hair.

The only negative moment I have ever had is in Hong Kong in a small local noodle sharp with shared seating. A couple walked in, the waitress gestured towards our table for them to sit on and they looked at me and immediately walked to another table. Obviously couldnt be arsed with the awkward social situation.
Fine by, we got a table to ourselves.

I might do TEFL first. Who knows, it's four years away. I wouldn't mind going to teach abroad and then coming back to do R34L T3ACH1NG afterwards.

Government propaganda caused (or at least perpetuated) that rather bizarre urban myth apparently.

I live and work in Manchester.  It's relatively affordable and pretty lively place but it rains all the time.  Also, there are certain places you should avoid if you don't enjoy being stabbed/mugged/shot, but no more so than most other major UK cities I think.

Pros: It's not London, Birmingham, Newcastle, Glasgow etc
Cons: It's not Edinburgh

Don't talk to the fans.

I sold my 3DS to Skerret.... Darn it.

Thanks for the tips. I think I'll say Manchester.
And doesn't it rain all the time here anyway?

Manchester is cool, but it isn't London.

If you've never lived in the UK before, surely the city recognised as one of the world's greatest would be a good place to be? It is expensive, but has more to offer than any other UK city just by sheer regard as to its size/history.

ShabbyMcCrabby wrote:

I sold my 3DS to Skerret.... Darn it. Thanks for the tips. I think I'll say Manchester. And doesn't it rain all the time here anyway?

No really, it rains ALL the time.

Cool though, however if I was given the choice I would work in either London, Dublin or Edinburgh (er...however they are possibly the most expensive places in the UK and Ireland)

Yeah, it didn't rain 'til later on, yesterday.

I lived in Mcr for 7 years. Completely brilliant place to live. Also not expensive unless you want to live in Didsbury or somewhere.