How to Turn Off Auto Sync on iTunes
Setting up your Apple device to automatically sync with iTunes after you connect the device to your computer and open iTunes is a way to ensure you won't forget to sync your device. However, if you download podcasts or add music or other media to the device after the initial sync, you will need to sync the device again. If you are confident you will remember to sync the device at the end of your session, you can avoid syncing multiple times during an iTunes session by disabling the Auto Sync option.
Click "Edit" in the Menu toolbar in the upper-left corner of the program window and then select "Preferences." The Devices dialog box opens.
Select "Devices" in the row of icons along the top of the dialog box.
Click to remove the check mark from the box to the left of "Prevent iPods, iPhones, and iPads from syncing automatically."
Click "OK." to save the changes and close the dialog box.