Turn The Phone Off
If you do not plan on answering the phone while you are sleeping or after business house, you turn it off. Do the same if you are in an area with no reception.
Stop Searching For A Signal
When in an area with poor or no signal, the phone will constantly look for a better connection and will use up all your power doing so. The best way to ensure longer battery life is to make sure you have a great signal where you use your phone.
Switch The Vibrate Function Off
Use just the ring tone, keeping the volume as low as possible.
Turn Off The Backlight
Either get by without it or shorten that amount of time to leave the backlight on. Usually one or two seconds will be sufficient.
Avoid Using Unnecessary Features
If you know it will be a while before your phone's next charge, do not use the camera or connect to the internet.
Keep Calls Short
This is obvious, but if you really need to conserve the battery, limit talk time.
Turn Off Buletooth
It will drain your battery very quickly. The same goes for Wi-Fi, GPS and infrared capabilities.
Use GSM Rather Than 3G
Using your phone is 3G/ Dual Mode will drain the battery quicker than if you just use GSM mode.
With a smartphone, avoid using moving or animated pictures or videos for your background. Use a black background when ever possible.
Be Net Savvy
When web browsing, use site like Blackl that display a black Google background instead of white.