A few short weeks ago, Apple held their annual Worldwide Developer Conference in San Francisco. As part of the event, they announced and showed off iOS 7... the newest version of their mobile Operating System. Later that day, it was made available to registered developers as a beta. Yesterday, beta 2 was made available (again, to registered developers). When will it be available? Apple says "this Fall". That much, we know. What we don't know is what the status is of new hardware (although we are starting to see lots of rumors).
My prediction is that we will see new iPhone hardware about the same time... September or October.
With that in mind, you may want to start thinking about how to prepare your iPhone to sell (or hand down to someone else). In short, there are three things that need to happen:
1) backup your current iPhone
2) erase all settings and data
3) remove and destroy the SIM card
Before you do anything, you need to ensure that your current iPhone is backed up. Hopefully, you are doing this already, but if not, you need to. You can either backup using iTunes (which requires either a physical connection to your computer or Local Area Network access to your computer) or via a free iCloud account. My personal preference is to use iCloud because backups happen automatically over the air once a day with no user action required. If you're using iCloud to backup, verify the current status by going to Settings > iCloud > Storage & Backup. The status will be displayed at the bottom of that screen. If you're using iCloud to backup, you will need to connect your iPhone to iTunes and check the status within the properties window of your device.
Resetting your device will ensure that all your data is gone from the device, and that it is set back to factory settings for the next user. To do this, go to Settings > General > Reset > Erase All Content and Settings (as shown below):
It will ask for your security code to confirm your approval, then ask you one last time (just to make sure). The reset process usually takes a few minutes. Once completed, your old iPhone is ready to sell!
The last step is simple, so I won't spend time on it. Suffice it to say, SIM cards (at least on AT&T) are a single-use component. Once it's been used for a specific number, it can't be used for another, and since you get a new SIM with your new phone, the old SIM is useless. Go ahead and trash it.
If you're in a bind and looking for a guaranteed buyer, check out www.gazelle.com. You may not get as much as you could from eBay or CraigsList, but it's a guaranteed sell. They also offer a 30-day price guarantee, so it's not a bad idea to lock your sale price in today, even if you don't want to give up your device for a month.