Back Up Your Device
The first step in the transfer of your Kindle's ownership is a complete backup of the files on the device. While Amazon keeps a copy of all electronic content that has either been purchased through Amazon or sent to the device via the Kindle's email address, anything that was transferred with a USB cable from a computer to the Kindle is not backed up on the Amazon server. To play it safe, connect using a USB cable and transfer everything -- even those documents you know are on Amazon's cloud storage -- from the "Documents" and "Books" folders on your device.
Deregister from Your Kindle
Deregistration ensures your device won't be connected to your payment methods, subscriptions or other content you've purchased from the Kindle Store. You can do this from the device itself by accessing the Settings menu. On Fire devices, touch the gear icon in the header of your Home screen and select "More." After selecting "My Account" on the next page, tap the "Deregister" button under your device. On non-Fire devices you can touch "Home | Menu | Settings | Deregister."
Deregister from Amazon.com
To deregister using Amazon.com, select "Manage Your Kindle" from the menu that pops up when you hover over "Your Account." From the left side menu on the next page, click "Manage Your Devices" under Your Kindle Account. Click the "Deregister" link to the right of your desired device.
Reset to Factory Defaults
Once your device is no longer registered to your Amazon account, reset it to factory defaults to clear all electronic content, preferences and personal information from the Kindle. To do this on a Kindle Fire device, navigate to the Home screen and tap the gear icon in the header to open the settings menu. Select "More," then "Device," then "Reset to Factory Defaults." On a non-Fire Kindle, tap "Home | Menu | Settings | Reset to Factory Defaults."
Register the New Owner
The new owner will need to have an established Amazon.com account in order to register the device in her name. Registration needs to be done from the device in order to properly send the serial number and wireless delivery information to Amazon. Locate the appropriate menu the same way you did to deregister the device, though you'll find the option now reads "Register" instead.