iPhone or iPad with an iCloud account? Sign out before getting rid of the device. Go to Settings > iCloud, then scroll to bottom and tap Sign Out. Press Sign Out again from the warning displayed on screen.
Remove SIM card (and MicroSD card if you use one). Run a factory reset; this will remove any files stored on the device, and erase any accounts such as Facebook or Twitter.
- On iPhone or iPad. Go to Settings > General and scroll down and press Reset. From here, select Erase All Content And Settings. If you have a passcode on the phone, you will need to enter that before the resest can take place.
- On Google. Go to Settings > Backup & Reset. From here, select Factory Data Reset, then Reset Phone on the screen displayed.
- On Windows. Go to Settings app and select System. Choose About, and press Reset Your Phone to make a factory reset.
- On a Windows tablet. Go to Settings > Update & Security > Recovery (in options on left hand side of screen). Under Reset This PC, tap Get Started, then Erase Everything from the options displayed.