Purchase or make a post card. To increase the likelihood of your secret being published on the Post Secret site, use a standard size post card. If you're making your own post card, the standard size is 4 inches by 6 inches. It should be a durable material, like heavy duty card stock so that it arrives in good condition.
Be creative. Put some thought into how you can combine your custom artwork or the post card you purchased into something that compliments your secret. You have creative liberties on that 4 inch by 6 inch square, you can paint, draw, paste and even use photos.
Share your secret. The fewer words you use, the more space there is to put those words. Use big, clear letters. In order to be chosen to be published on the Post Secret site, post cards must be easily legible.
Stamp and mail your postcard. Check the USPS website for current standard postage rates and mail your post card to 13345 Cooper Ridge Road, Germantown, Maryland, 20874.