I'm still in the process of looking into this myself, but JET seems to be a good option in terms of pay and support if you don't mind the crazy long application process and possibility of being placed in the middle of nowhere. There are private gigs around but seem to in general pay quite a bit less and you'll more than likely have to set up a lot of things like where you'll live on your own - but then you have a choice in where you end up and don't have to spend 9 months stressing over applications.
If you want to teach English as an occupation and not just for a year or two, then studying teaching would be a good idea and will probably give you more options (and pay) in terms of private jobs
