The first question is: 'Why do you want to come (here)?' Some people come for the money (but not many come to China for that. You can save here, but you are not going to save a fortune). Some come for the experience (and it *is* an experience) and others come thinking of it as a long holiday. If your thinking of it as the last one, then my recommendation is don't.
If you come here for the experience, and come with an open mind, then you will certainly experience things that you will remember for a looooong time to come!
Research your school as well as you can. Ask for the contact details of the foreign teachers already there and, even better, those recently left.
Make sure you have ALL the details up front and in writing. Keep printouts!
Make sure you have enough money to go elsewhere if it doesn't work out (worth having a job offer or two as backup places).
The question you need to ask of the school is: "Can you give me a Z-class visa?" If they can't, don't go there. Ask the other FTs if they have one.
There are lots of things to look out for, but you can make it work and have a good time as well.
If you need any more info feel free to e-mail me.

*NB* The above covers China only! Can't speak for Japan or Korea!

> Hi
> I am an Aussie high school teacher thinking about heading over to
> either China or Japan to teach. I have been offered several positions
> at universities in China offering around 4000/month and in Japan
> through NOVA agency. I read a lot of negative stuff on this forum and
> wondered whether I should head over or stay put in Brisbane? Is it
> worth it? Do you save any money? I am not a pretty blonde so will I
> be fired as soon as the see me? etc... Any advice would be much
> appreciated.