Planning to sell iPad 2 - need to know how to securely erase data I did a Google search and I have followed instructions from this link: http://www.macworld.co.uk/how-to/iosapps/how-wipe-all-personal-data-from-iphone-ipad-3498379/

Is that all I must do? Are there any other things I need to check before selling it?
I think you are good to go. If you are concerned about recovering data, it is almost impossible to recover the data after the encryption key has been deleted (that's what Erase all content and settings does). You can check at http://support.apple.com/kb/ht5661 to make sure everything is good.

TL;DR: Good to go. Nothing else needs to be done.