A lot of "free" games make money by charging for in-app purchases. This can be costly for iPad owners, especially when kids use their parent's credit card without permission. Luckily you can keep other people (or yourself) from running up your App Store bill by blocking any in-game purchases on your device. Here's how:
1. Navigate to Settings -> General -> Restrictions -> Enable Restrictions
2. Enter a passcode for Restrictions. You will be asked to enter it twice.
3. Scroll down to the Allowed Content section.
4. Select In-App Purchases -> OFF.