This is one of my "How-to's"
How to make your battery last longer
Go to Settings→Display→Brightness→Uncheck Automatic brightness and slide the little slider thingy-ma-jig all the way down (to the left)→Hit OK
Still under Display→Screen Timeout→Turn it down
Stay in Settings→Location & Security settings→Uncheck “Use wireless networks,” “Use GPS satellites,” “Enable assisted GPS.”
Again while in Settings→Wireless & networks→Uncheck “Wi-Fi” and “Bluetooth”