1. Lower the Screen Brightness -With how bright the iPad 2 and Pad 3 displays are, you can usually get away with 60% brightness at all times. At night, going down to 30% or 40% brightness or less is easier on the eyes and will conserve even more battery. Access the setting by double-tapping the home button and swiping to the left.
2. Turn Off Notifications -Disable Notifications for apps you don't absolutely have to have notifications posted for and you can recoup some battery life. Find this in Settings > Notifications, and disable them.
3. Disable Bluetooth - If you aren't using Bluetooth for an external wireless keyboard or otherwise, keep it disabled.
4. Use Airplane Mode - When doing something that doesn't require internet access, turning on AirPlane Mode can save some battery life. Perfect for reading books or doing things on the iPad, and it has the added bonus of preventing internet distractions. Find this in Settings > Airplane Mode.
5. Disable Location Services - Most important for 3G/4G iPads, but you will save battery life even if you just have a Wi-Fi model. Turn these off in Settings > Location Services.
7. Disable Diagnostic & Usage Reports - Sending out usage and diagnostic reports helps Apple to make a better iOS experience, but it also causes some minor activity in the background. Disable it for maximum battery conservation. Find this in Settings > General > About > Diagnostic & Usage > Don't Send