1. Turn off apps when not in use. These include WiFi, Bluetooth, NFC and GPS .
2. Turn on power saving
3. Adjust Brightness
4. Install clean master
If you use the Galaxy S3 for SMS and calls only, set the network to 2G instead so you can save more power. Several apps are now capable of sending SMS and performing calls using the Internet.
Restart the smartphone every after full recharge to free memory on the RAM and get a more accurate battery reading. Restart can also fix minor bugs you are not aware of.
Your device doesn't feature an unlimited number of storage and it is best to transfer old photos or videos to a computer. More files being indexed by the processor can eat away battery life.
Drain the battery until it turns off on its own then recharge it fully without any interruption or usage - it may take three to four hours to complete. Do this every week only not everyday because it can cdamage its overall life based on the discharging and recharging cycle. When you have the charger, plug it in during low battery level. Your cellphone will notify you when to plug the charger.
9. If all else fails to prolong the battery, better buy a new battery to save you from the headache.