If you are thinking about selling your iOS 7 device (iPhone, iPad or iPod Touch) then you need to follow the directions below BEFORE you sell your device.
1. Go into the "Settings" on your iOS device and turn off "Find My iPhone". This can be done by navigating through the following menus within "Settings":
Settings > Privacy > Find My iPhone (or iPad, or iPod depending on your device type)
When you turn on "Find My iPhone" in iOS you are also turning on something called "Activation Lock". Activation Lock is a theft deterrent that Apple built into the iOS 7 operating system. Once activated the device can't be wiped or have it's settings significantly changed unless the iCloud account password associated with the device is entered first. So if someone stole your iPhone and tried to wipe the device so they could use it they wouldn't be able to do so unless they also had your iCloud password.
2. Next you need to completely wipe the device. This can be done by going into:
Settings > General > Reset
and choosing "Erase All Content and Settings."
3. To be sure that your deceive is no longer Activation Locked (if you have another iOS device), use another iOS device and use the app "Find my iPhone". If your aren't already signed into your iCloud account you used on the device you just wiped, please do so. Once signed in go to the "My Devices" tab and make sure the device you just wiped in NOT listed there. If it is listed there, select it and then select the "Remove from Account" option. This will do the same thing as step 1 listed above, it turns off Activation Lock on the device.
If you don't have another iOS device, go to iCloud.com and sign in with your iCloud account email address and password. From there you can get into the "Find My iPhone" app just like you were on another iOS device and follow the same instructions I just listed above to ensure Activation Lock is removed from your old device.
4. The last step isn't required but is a good idea to do. Go to the Apple Support Profile Website (https://supportprofile.apple.com/MySupportProfile.do), login using your Apple ID and go ahead and remove the device you are selling from you profile. This profile is used whenever you call or go into an Apple Store and get support or service on your device. Removing it from your profile will make it easier for you and the Apple genius to determine which device you need help with if you don't have a bunch of old devices you no longer own in your profile. If you never registered your device with Apple then it won't show up here.
The reason I am posting about this is because I failed to follow these exact steps when I sold one of my devices and I had to remotely remove the Activation Lock from the device after the fact (which is step 3 above). Apparently just performing step 2 above DOES NOT remove Activation Lock from your device, even though this has been described as doing a "factory restore" for many years now. With iOS 7 and Activation Lock a complete erase of all content and settings in no longer restoring your device to factory conditions because it is still Activation Locked. I did a lot of searching for information on the web about this and there is a lot of bad information out there. Many sources claim that just performing step 2 above removes the Activation Lock, but it does not. You must perform step 1 first but verify with step 3 just to be sure. Hopefully this keeps you from making the same mistake I did...