Well... Where you go depends on where you get a job.
Where you get a job depends on the method upon which you get a job.
If you come to Japan first (I'd recommend Late February early March) on a work vacation visa you can apply to schools (High/Jr/Elem) and have a job by April. You may get stuck at an Eikaiwa (lots hire around this time too since Juku really kicks up around April) because of a lack of experience.
The more Japanese you speak the Better. If you are really, REALLY Fluent then schools will be more interested in you (like native fluency) you can also get in at jobs like translation, editing, IT, and possibly Trade (Especially if you speak more then just English and Japanese) The more you speak the easier you'll find everything anyways.
Anyway I've got a lot of info up on my Blog if you want to check it out. It has a bunch of job search links, some Eikaiwa reviews and the process I went through to get a job here.
Somewhere over the Ramen Bowl