To stop iTunes from automatically syncing every time you plug your iPad into the computer, follow these steps:
1. Open iTunes on your computer.
2. From the top menu select iTunes -> Preferences (in Windows choose Edit -> Preferences)
3. Click the Devices tab.
4. Check the box next to Prevent iPods, iPhones, and iPads from syncing automatically.
Now your computer will not auto sync every time the iPad is plugged into a USB port.