The Battery Lite app shows your battery level in percent and provides hints on how to improve your battery life.
1. Turn off Bluetooth.
2. Turn off Push notifications.
3. Turn off Push Mail.
4. Turn off auto-check of Mail.
5. Turn off Location Services.
6. Turn off Wifi.
7. Minimize playing of games.
8. Turn off the iPod Equalizer (EQ).
9. Turn off 3G.
10. Use airplane mode in low or
11. Turn down the screen
12. Lock your iPhone.