If you are looking for selling your old smartphone or tablet, there are some things you must do before the sell. It's vital to clean your device as there won't be any information left on the device. No matter who you sell it to, it's important to wipe it out of any data, as you will protect your own privacy.
The first step is to remove the SIM card. Yeah, I know sounds stupid, but it's a fact that people forget their SIM card in phones when they sell it, so you can loose all your data.
If your handset has a microSD card, you must take it out. You can do that by pressing the "Safety remove" button in the Storage and External Memory menu.
If you sell the device with a mciroSD card, you must format it before you give the device to the new owner.
Now looking at the internal memory, you must restore the device to the factory condition. So, after you download all your data on another device, you restore the smartphone, so there will not be any copy of potential harmful information. If you have a microSD card you can save all the information there or you can use a USB to connect to a laptop and download them there.
To restore the device you select Setting menu, Backup Settings and press "factory data reset". This process will remove all Google account settings, pictures,music, other user data or other installed apps.