Lifehacker puts out good stuff quite often.
Folks buy and sell their devices often enough that it’s worth noting three excellent articles about this topic.
If you have additional suggestions, please add them!
The first is…well the titled source: http://lifehacker.com/the-apps-you-need-to-deauthenticate-before-selling-your-1629748753
The second is your phone: http://lifehacker.com/5808280/what-should-i-do-with-my-phone-before-i-sell-it
The third and arguably the most important is your computer: http://lifehacker.com/5966580/what-should-i-do-to-my-computer-before-i-sell-it
Anyway…these are some good things to at least bookmark so you’ll have them when the time comes.