Write the address of the recipient on the front, center of the envelope. Start with his full name (starting with Mr. or Ms.). The next line should include the building number. The following line should contain the building name. Conclude the address with the city or locality and ZIP code. On the final line write INDIA. This designates it is exiting the United States.
Write your address on the back of the envelope as a return address. Include UNITED STATES under your address because the mail is being sent outside of the country.
Visit your post office. Ask for an air mail stamp to send the card to India. If the envelope is an odd shape, be sure to have the postmaster weigh the envelope to make sure the proper postage is included. Non-average-sized envelopes may charge more due to hand processing.