1. Turn off your Bluetooth
2. Disable sounds and vibrating alert
3. Brightness – lower the brightness of your screen
4. Setting the Power saver time-out and the Light time-out to the low values will help too (you’ll find them in the display settings)
5. If you are not using an application switch it off – you’ll get a list of all active applications by long pressing the menu button
6. Games – it’s fun to play games on your way to school/office but they are power-hungry beasts; I can’t tell you not to play games but think about your battery when you are playing.
7. Turn off your phone when your phone has no signal coverage.