Most people want their iOS devices to sync with iTunes each time they connect the device to their computer. But sometimes you don’t want this to happen. If you’re one of the many people suffering from iTunes sync problems, you may want to connect your device to charge it, but not sync. Here’s how you can change this setting.
First, select your iOS device. You’ll see an icon at the top-left of the iTunes window, to the right of the media kind icons; click it.
Next, click Summary in the sidebar. On the Summary screen, you’ll see some options:
Uncheck Automatically sync when this iPhone [or iPad, or iPod] is connected.
After you do this, click Apply at the bottom of the window. In the future, your device will only sync when you want it to. Connect it, select it as above, and click Sync at the bottom of the window.