1. Adjust Screen Brightness - Brighter light will consume more battery when compared to a lesser bright light. You can lower down the brightness of your iPhone 4 from Settings > Brightness.
2. Turn Off -
a). 3G - You can browse super fast with the help of 3G, but I’ll recommend you to turn it off when it is not in use. This will surely add up another boost to your battery backup. To turn on/off 3G open Settings > General > Network.
b). Wi-Fi - Wi-Fi is really a nice way to stay connected to the internet, but make sure to turn it off when you’re sleeping or when the Wi-Fi is not in use. To play with Wi-Fi settings, open Settings > Wi-fi.
c). Bluetooth - Bluetooth (when switched on) consumes a lot of battery. It is not always required, so you can keep it off for most of the time to save your battery. You can switch it on/off from Settings > General > Bluetooth.
d). Sounds and Vibrations – You can turn off the unnecessary sounds and vibrations to save your battery. For eg. you can turn off the Lock Sounds, Keyboard Clicks etc. To play with sounds and vibration settings, open Settings > Sounds.
e). Notifications - If you’re using an application which keeps sending you notifications, disable or uninstall it to save battery life.
3. Close Applications - As you all know, iPhone 4 supports multitasking, so remember to close an application when it is not in use.
4. From 0 to 100 - Empty your battery at least once a month and charge it back to 100%. This is one of the best ways to get the most out of your battery.
If you follow these tips, you’ll surely be able to save a lot of battery life. If you’ve more tips in mind, use the comment box to share them with us.