Sending letters to Japan and Mailing from Japan?

1. What is the format for sending letters to japan from the United states?
Can you give me a sample address and what to put for
the return address?

for example to Japan is it:
Mr. blahh
address
Hirakata-shi Osaka
5730127 JAPAN
AIR MAIL

for the return address from US:
Mrs. blah
address
City, State, Zip code
United States

MY question is do you have to put United States at the end of the US return address.
2. And What is the format for sending letters to the United States from Japan?
Can you give me a sample address and what to put for
the return address?

Oh anyone who answers me first and with good marks I'll give them max points!

Everything you have is correct.
Some people put JAPAN on the final line (it doesnt matter).

You don't have to write "AIR MAIL" right at the bottom, actually when mailing from the USA you don't even need to write "via Air Mail" anymore.

For the postal code of Japan part, proper format is a hypen after the first three numbers, so it would be something like 573-0127

Hirakata-shi then a comma ","
Hirakata-shi, Osaka

In fact you don't need to right -shi (-shi means city) so you can leave it as Hirakata, but again, it doesn't matter.

Sometimes people put the postal code and the country name on separate lines of their own, but again it doesn't matter, I've done it both ways.

As long as the postal code is correct and address, you won't run into much trouble.

Your return address in the USA is right. If someone mails from Japan to the United States they would right it exactly how you have it. If you want to keep it proper, the zip code is just fine.
US mailing manual requires postal code precede country name.

For sending international mail, as long as the country's English or French name is written in alphabet letters, the address part can be written in the country's native language (even in kanji or another writing system) and it will go through ok.
So if you send a letter from the US to Japan, it's ok to write:
銆?01-8501浜兘搴滀含閮藉競鍗楀尯涓婇偿缇介壘绔嬬敽11鐣湴1
Japan

It will go through ok! You can write it in alphabet letters too of course, they will handle it no problem. It can be in Japanese order (just write romaji instead of kanji) or you can write it in English order like your example above, either is ok. They are pretty flexible about it.

Going to the US, write the destination address just like a regular US address and put "USA" or "United States of America" on the last line of the address, it should go through fine. For the return address, its the same as above, either kanji or alphabet is fine as long as you write "Japan."

In Japan a mailing address typically starts with the Postal Code. However, JAPAN POST has such an advanced system, and has become so used to overseas mail, that even the order no longer matters.
for ex.: 123-1234 or: My Friend
My Friend xxxx cho
xxxx cho Edogawa-ku
Edogawa-ku Tokyo, Japan
Tokyo, Japan 123-1234

It is even okay to fit the entire address details on just 3 lines.
As for the return address, it is always a good idea to use the country at the end of the return address to avoid mail being sent to a city of the same name in a different country.
I would write the return address in the following sequence:
Name
street address
City, State (abbreviaton)
USA
ZipCode

The reason for the ZipCode being on the last line is that PostOffice equipment is set up to automatically scan the bottom inch or so of the envelope for this code.