What to do with your old Android phone before selling it

[johnypowas]

Clean it
Once the insides of the phone are clean, the next thing you should do is clean the outside too. There might not be much you can do about scratches on the screen or general wear and tear, but you can sell it off without grubby fingerprint marks all over the display.
If you want to impress a potential buyer, you could apply a screen protector and replace the battery cover (if there is one).