1. Store and use the iPhone at room temperature:
Direct sunshine or putting the Phone in the glove compartment of a warm car will cause your iPhone’s battery life to drop sharply. The Phone functions well between 0 degrees centigrade and 35 degrees centigrade (32-95° F). You should store your Phone in conditions between -20° C and 45° C (-4° F to 113° F).

The ideal battery life environment for both usage and storage is room temperature: 22° C (72° F).

2. Mail Auto-checking:
Change mail auto-checking from 15 minutes to 1 hr or turn it off.

Go to Settings
Click on Mail
Click on Auto-check and increase the interval or turn it off altogether

3. Turn off Wi-fi:
If your mobile offers Wi-Fi but you don't use it constantly then you will get better battery life by turning it off and then enabling it when you want to browse via a hot spot.

Go to Settings
Click on Wi-Fi
Click on Off

4. Turn off Bluetooth:

Go to Settings
Click on General
Click on Bluetooth
Select Off

5. Reduce the display’s brightness:

Go to Settings
Click on Brightness
Drag the slider to the left to dim the display’s brightness

6. Enable the display’s Auto-Brightness:
Alternatively you could enable Auto-Brightness so the Phone’s display is automatically adjusted to match the current lighting conditions:

Go to Settings
Click on Brightness
Set Auto-Brightness to On

7. Lock the Phone:
It may sound obvious but locking the iPhone as soon as you ’ve finished using it will turn off the display immediately and ensure that it won’t be making persistent calls while it’s in your pocket. Simply click on the Sleep/Wake button on the upper right hand of the Phone.

8. Enable Auto-Lock:
Better still, if you can get into the habit of locking your iPhone yourself simply turn on the Auto-Lock feature:

Go to Settings
Click on General
Click on Auto-Lock
Select a duration before the Auto-Lock kicks in, eg 1 minute or less

9. Turn off keyboard clicks:
If you regularly use the Phone’s touch keyboard then the constant need to generate audio keyboard clicks can add to the Phone’s power consumption. To turn off keyboard clicks:

Go to Settings
Click on Sounds
Turn Keyboard clicks to Off

10. Turn off the music equalizer: (EQ)
The Phone’s audio equalizer may add some oomph to the songs but it also delivers a powerful blow to the handset’s battery life because of the constant processing it require