How to save my iPhone 4 battery?

It takes forever to charge but dies fast, like less than 5 hours. My brightness is medium

There's an app I downloaded from the App Store. It's free and it's called battery doctor. It is amazing the change it makes on your phones battery life. All you have to do is keep it running while your charging your phone. Works best when your phone is completely dead. There's info in the app telling you how to conserve your battery.