I Got a Bisa, How 'bout you?
 

MOFA: A Guide to Japanese Visas - Documents to Be Submitted with Visa Applications

Instructor
Documents certifying the academic career or a copy of an educational license of the person concerned.
Documents certifying the professional career of the person concerned.
Basically what this amounts to is proof of your education and/or career as a teacher. Note that TESL certificates do not alone qualify you to teach in Japan no matter how they are promoted. A degree would be a different story because it is not a certificate.

Specialist in Humanities/International Services
Materials describing the business undertaken by the recipient organization.
A diploma or a certificate of graduation with a major in a subject relating to the activity of the person concerned, and documents certifying his or her professional career.
Proof that the company hiring is in the business of hiring teachers/ALT's. Now the second one about "major in a subject relating to the activity of the person concerned" is not enforced word for word. Why else would most ALT's I know be computer science majors? Basically all you need for this one is a degree which is why most teachers fall into this category. They're foreign, they went to school, why don't we make them a teacher?

Short Term Teaching
 

Removed for the fun of it.

Finding a job before or after you come to Japan
 

Read above.

Types of Teaching
 

More of the same.

To JET or Not
 

Simple answer is, yes.

Killed this one too.

thanx!..
u interested me

Removed for the fun of it.

Does anyone know if Jet will fly you family over as well or will they only pay for the employee?

No I don't think they do, but then I've never met a JET that was married.