1. Turn off Wifi, GPS, NFC, Mobile data, Bluetooth when you don't need it.
3. Make your screen timeout less. If you put down your phone, 1 minute later you should make the
screen turn off. Any later and battery life is affected.
If you're too lazy and/or don't want to read a list of 4, the power saving feature on your phone accomplishes most of this already. The worst case scenario is you have a faulty phone battery. Take you phone to a local repair center to further delve into the issue.