Play Coins are new feature to the 3DS, and are earned by walking around with your 3DS in sleep mode.
Similar to the Pokewalker addon for the original DS, the 3DS has a built in motion tracker that will count your steps while the 3DS is in sleep mode. Nintendo seems to be into trying to get kids active by giving them these incentives.
You earn them fairly quickly, at about 100 steps per coin. The value of the coins depends on the game. Some games so far only need about 20 coins to unlock certain items.
There is a cap on the amount of coins you can have at once, which is currently set at 300 coins.
Honestly, 100 steps isn’t that much and you can rack up these points fairly quickly just by your normal day to day walking. So, put your 3DS into sleep mode and throw it in your pocket and go about your business to earn as many points as you can.
Or.. tie it to your little brother or your dog (be careful with this one) and sit on the couch watching your points go through the roof.

Xune September 18, 2012 at 11:37 pm
it wasn’t hard to figure out people i figured it out as soon as i bought the system
Toastyy1990 April 30, 2012 at 9:59 am
So far, I’ve walked 4000 steps today, and earned 10 coins. Are you sure it’s 100steps = 1coin?
liam May 11, 2012 at 6:40 pm
its a 10 coin limit a day
but it is 1 coin for 100 steps
Toastyy1990 April 29, 2012 at 2:23 pm
Thanks for the info; I’ve been wondering how to earn these. Looks like it’s time to start taking my 3DS to work with me!
dasf April 12, 2012 at 8:31 am
Yeah i didnt know you could get them from walking…
lucas March 20, 2012 at 8:36 pm
thank you i dident now how to get play coins untill i found this site and im just 12 thanks