Addressing a postcard properly ensures that the card reaches the desired destination, without issues. Besides knowing how to spell out your address and the recipient's, keep the address in certain areas on the card, otherwise a postal sticker or bar code may block crucial information.
A return address -- your home address -- goes on the upper left-hand corner of the card. Include your name on the first line, your street address on the next, and the city, state and zip code beneath that. If you are mailing the postcard to an address outside of the United States, include "USA" in your return address. Both the return address and mailing address -- along with a written message if any -- go on the address side of the postcard, which is the side without a printed image.
Addressing the Recipient
Spell out the complete name and address of the recipient, just as you did the return address, on the middle of the right side of the postcard. Keep the entire address -- including the country and postal code if you are mailing to a foreign address -- at least 3/4 inch above the bottom of the card if possible, as the bottom space is used by the post office for a bar code. Keep the address area limited to a 4-inch-wide space that is 2 inches high, slightly away from the bottom and right edges. If you are including a written message on the postcard, keep the message away from the upper-left corner as well, as this space is reserved for a stamp or postage sticker.