App hanging

Try double tapping the Home button, pressing down on the appropriate app in the bottom task bar until a red minus sign appears, then press on it!,

Force app to close

Hold down the Sleep/Wake button on top of iPad for a few seconds until a red slider appears, then hold down the Home button until the app closes

You can try this as well.

Force quit the app by holding down on the sleep button until the red slider appears. Let go of the sleep button and then hold down on the home button until the app quits.