Anyone who's looked at the Apple TV for even a short time will notice something: there are no buttons on its case. So, how do you turn it off?
Well, just like the iPod, you don't turn the Apple TV off per se, as much as put it to sleep. Because there are no buttons on the case, you can only do this using the remote.
To put the Apple TV into Standby mode, click the Menu button on the remote until the main menu is onscreen.
Scroll down to the last option in the left column, Settings. Choose it.
Scroll down to the last option in right column, Standby. Choose it.
You'll know the Apple TV is in standby mode because the white light on the front of the case will turn off and it will stop sending video to your TV.
Wake it up by clicking any button on the remote.