This video is only applicable to those who have NOT updated their iPhone/iPad to iOS 7 or 7.1 Please see additional videos for iOS 7 and higher.
As with any mobile device, it’s possible to forget where you had it last. “Find My iPhone” (this app specifically says “iPhone” but works for iPad and iPod Touch as well) shows you the approximate location of your iPad on a map. You can also play a sound to help locate the device if it’s nearby, remotely lock the device, or as a last resort you can erase all the information from the lost device.  You can also use “Find My iPhone” from your computer by visiting www.icloud.com.