Instructions
Plug in your Nintendo DS power cord. Make sure the charging light turns on to ensure that the DS is charging.
Turn on your Nintendo DS and load your "Nintendogs" game. Choose a dog and select the brush icon to groom him.
Place the brush icon directly on the center of your dog with your stylus. Take the stylus off the screen without removing the brush icon from your dog. If performed correctly, the dog will still have the brush over it.
Leave your Nintendo DS running with the brush on your dog while you're out or when you go to sleep. The Nintendo DS will enter into sleep mode after a few minutes, but the game will still be running.
Finish grooming your dog by removing the brush icon. You'll receive several hundred trainer points depending on how long you left the brush on your dog. Repeat this process every time you go out or go to sleep to earn thousands of trainer points.