How to unregister iphone before selling it

Settings>General>Reset>Erase All Content and Settings

settings --> General --> reset --> Erase all Content and settings.

I suggest you read the manual: http://support.apple.com/manuals/

You need to erase it as mentioned above but you don't need to 'unregister' it. Just erase it and sell it.

No, you do need to unregister it otherwise the user will not be able to use the 'find my iphone' option via icloud. I have passed my first iphone on to a family member and in icloud both devices come up with my name and not his. I initially thought restoring it and renaming the iphone would suffice. If I had've sold it on, the individual most probably will have not had the benefit of using this option for themselves.

Not true. After "Erase all Content and Settings", the new user can (and should) setup iCoud and Find my iPhone for themselves. Just a like you did when you first got it.

Do you need to unlock the phone before selling it or will the erase method above do that? I have an ATT iphone 4. Do I need to unlock it if the buyer is going to use it with ATT or Tmobile?

beedoola wrote:

Do you need to unlock the phone before selling it or will the erase method above do that? I have an ATT iphone 4. Do I need to unlock it if the buyer is going to use it with ATT or Tmobile?

Only ATT can unlock the phone if it's going to be used with T-Mobile

what it someone else with ATT is going to use it? then no need to unlock it?

Do I just erase the iphone 4 and sell it?

I agree. It is just like setting it back to factory defaults. Just like on a notebook or MAC.