Deleting All Data before Selling an Samsung Galaxy Phone

The simple delete or Reset, can't make sure the data safe, it can be recovered by some android data recovery.

If you want to permanently erase data from Samsung Galaxy Phone,like Samsung Galaxy S4, Samsung Galaxy S3, Samsung Galaxy S2, Galaxy Note 4/3/2 and Samsung Galaxy Ace,ect, I think better use a third-party to erase all data.. If you use a professional data eraser for android,no data recovery can get them back.

It is essential for users to wipe out all data before they give their handsets to another owner. As for those who want to make sure nothing of their previous details get left behind, here are some tips.
1.      Backup Important Data
-Before deleting all files, you should have a backup of all your precious photos, videos, contacts, and other data that is important for you. When you buy a new Android phone, you can use the same files that you backed up to restore the data on your new phone.
2.      Back Up Your SD Card and Internal Memory
-Connect your phone to your computer and transfer all the contents of your Android phone's internal and external (SD card) memory to your computer. You can also delete from the SD card to clear all the data inside.
3.      Format your SD Card and your phone's Internal Memory
-After backing up all of your files, ensure that you have saved them all in your computer. Proceed to format your Android phone's internal memory and its SD card. To format SD card for Android devices with an external SD card, there will always be an option to "format SD card", while Android devices with only internal memory would have to manually remove files from its SD card, and then use the Factory Data Reset option to wipe the contents of the phone.
To Format SD card in Android 4.0 and above, head to Settings > Storage. Tap on "Unmount SD Card", and then tap "Format SD card" to clear out the data from the SD card.
4.      Factory Data Reset
-Head to Settings > Privacy > Factory Data Reset. The Factory Data Reset option in Android phones will bring it back to factory settings, as if the phone has been untouched. It will not erase data on your SD card, which is why it was mentioned above to wipe the SD card's data. The reset will erase all data on your phone's internal memory including your Google accounts, downloaded apps, photos, music, and other data.

Deleting All Data before Selling an Samsung Galaxy Phone

How do I Delete all my Personal Information from my Samsung Galaxy

To delete all of your personal information from your device, from the Home screen, press Menu Menu key

> Settings Settings Shortcut

> Back up and reset > Factory data reset. Read the information provided, and then touch Reset device > Delete all.

The process may take a few minutes while your device removes your personal data and restores the Android™ platform to its original state.

Important! Your personal information cannot be recovered after using this feature. Please save any personal information you need to your computer before using this feature.