How to Get Better Battery Life for Your cellphone

Turn the phone off. This will probably be the most effective and simple way of conserving your battery’s power. Why? This will help conserve energy and also charge your phone. If you don’t plan on answering the phone while you’re sleeping or after business hours, just turn it off. Do the same if you are in an area with no reception (such as a subway or remote area, since constantly searching for service depletes the battery fairly quickly.) Some phones have an automatic power save feature, but it takes about 30 minutes with no service to kick in. By then, much battery power has been used. If you don’t need to receive or make calls but are using a smartphone as a PDA, disable the phone functionality (flight mode).
Stop searching for a signal
Switch the vibrate function off on your phone, using just the ring tone.
Turn off your phone’s back light.
Avoid using unnecessary features.
Keep calls short
Turn off Bluetooth
Same goes for WIFI, GPS, and infrared capabilities, if your phone has these features built in. Keep them off except when you need them.
Turn the brightness of the display to the lowest setting possible.
Use GSM rather than 3G – Using your phone in 3G / Dual Mode will drain the battery quicker than if you just use GSM mode – have a look at your phones spec and you’ll see it will quote two different battery life times – normally 50% more for pure GSM use.
With a smartphone, avoid using moving or animated pictures or videos for your background.
Use a black background whenever possible.