On my Animal Crossing: New Leaf, the T&T store is selling Fortune Cookies for 2 Play Coins. I went to my home screen, and realized that I had 1 Play Coin. How do I obtain more Play Coins?
You obtain Play Coins by walking around with your 3DS in Sleep mode. If your 3DS is turned completely off, it will not count.
For every 100 steps you take, you earn one coin. You can only earn 10 coins per day, even if you take more than 1,000 steps. You may only hold a maximum of 300 coins at once.
An easy way to earn them if you're not going out for the day is just stick it in your pocket as you walk around your house. You'd be surprised how many steps you take in a day just doing daily things inside.
Alternatively, you can rhythmically shake it and that apparently works, but it's usually a better idea to just do some walking.
Play Coins are a feature on the Nintendo 3DS. The player can obtain them by walking; players earn 1 coin for every 100 steps taken and can earn 10 coins daily, for a maximum of 300 in their bank at any given time. You can also get Play Coins by shaking your 3DS. Plus, if you change the date, you can get more than 10 Play Coins a day. The player can then use them to purchase applications and special content for his/her Nintendo 3DS.