First of all, open iTunes.
- On the menu bar, across the top left, click on Edit.
- Go to the bottom of the list and click on Preferences....
- In the pop-up box, click on the Devices tab.
- You should see check box beside the words: Prevent iPods, iPhones, and iPads from syncing automatically.
- Make sure it's checked.
- Now connect the iPhone to the computer.
- Once the iPhone appears on the left panel of iTunes, right click.
- Click on Transfer Purchases.
Anything on the iPhone that was downloaded from iTunes should be transferring to your computer.
Now to sync your iPhone, bring it up in iTunes and click sync at the bottom right of the screen, or go back into Preferences and turn back on automatic syncing.
Myself by doing a thorough examination of iTunes and from past experience.