To correctly address a piece of mail, clearly write or type your address in the upper left hand corner and the address of the recipient in the middle of the envelope. All information should appear on the front of the envelope (the smooth, flat side with no flap) and parallel to the longest side.
Your address, also known as the return address, can be a home or post office box. On the first line, you may write your name. This is not required by the postal service, but it provides your identification to the recipient. On the second line, list your street number, street name and apartment or building number if applicable. If using a post office box, write "PO Box" and the number on this line instead. On the third line, list your city, the proper two-letter state abbreviation and zip code. You can find a list of street and state abbreviations as well as zip codes on the USPS website.
The recipient's address uses the same format. The only difference is that the name of the person or business is required on the first line. According to the U.S. Postal Service, all writing on the envelope should be easy to read from an arm's length away and should not include any punctuation marks, such as commas or periods.