These tips work for me; they may or may not work for you.
1. If you are not using either GPS or Bluetooth, turn them off. This is easily accomplished using the pull-down notification panel. They are easily started again when you need them.
2. Keep your screen as dim as possible, while maintaining legibility. If you use your phone mostly indoors, you'll be amazed at how low you can set it. Again, use the notification panel to do this.
3. If you spend long periods of time reading an ebook or using another app that requires little Internet access, consider placing your phone into Airplane mode for that period of time.
4. I find that if I use my phone intensely for several days, I can feel the phone heating up and battery life drains rapidly. So I make it a practice to turn my phone off and then back on every couple of days.
5. Use a system tuneup tool such as All-in-One Toolbox to keep your system configured correctly. Uninstall apps you never use and configure which apps need to be launched at startup.
I hope this helps....