What is the proper way to address and envelope when......?

you have a person's name, ext. number, business name, room(or apt) number, street address, city, state, and zipcode. what is the correct order they should be written on the evelope?

On the envelope....

>> Business Name (if sending to a business/company, if not, then you do not need to add the business' name)
>> Attn: < Person's Name >
>> Street Address, Suite Number OR P.O. Box
>> City, State and Zip

Example:

ABC-123 Co.
Attn: John Smith
1234 Main Street, Suite # 1
Somewhere, CA 01234
--------------------------------------...
On the Letterhead:

(Centered OR Aligned Right)
>> Your Title & Name
>> Street Address
>> City, State and Zip
>> Your Phone Number (Home/Office/Fax)
>> Your e-mail

(Aligned Left)
>> Their Title & Name
>> Street Address
>> City, State and Zip

BUSINESS NAME
ATTN: PERSONS NAME
STREET ADDRESS, APT, ROOM OR SUITE #
CITY, STATE ZIP CODE

I would just put the Business name and then under it ATTN: persons name followed by the mailing address, city, state, and zip....no need for all the rest....it will make your envelope look sloppy.

Person's Name here
Company Name here
Address here, Room/Apt. # here
City, State and Zip here

That's all.

Business Name
Att: Person it is going to
Number, Street
City, State ZIP

I would do it like this....if the address is of the business.

Business name
Attention: Person's Name
Street Address Apt #
City, State Zip

If the extension number is just the phone extension number.....it shouldn't be included.

Name,(line 1)
Buisness Name(line 2)
street address- apt number(line 3)
city, state, zip(line 4)

Mr. John Doe
First Flight Recreation
3344 Lake Street - Suite 1314
Las Vegas, Neveda 12345

Business Name
Street Address
City, State, Zip
Attn: Insert persons name and department here

This is the Business way to do it, if you are sending an informal letter then you can put the business name first then Attn: whomever under it. I always do this the business way just to make sure the letter gets where it needs to go.