Go to settings > general > about phone > software info > and then tap 'build number' 3 times to enable developer mode. Then go back to settings > general > developer mode > and then scroll down until you see "window animation scale, transition animation scale, and animator duration scale. Now turn them all off. Now watch how fast and fluid your OS will be! I do this for all my other android phones, a huge improvement in speed when navigating through the OS.
Then go to settings > networks > mobile data > and then go through your apps and pick the ones you DON'T want to have background data permissions (such as Facebook) and then press disable background data. It'll help you save battery and data. Alternatively you can enable "data saver mode" as well from the notification bar dropdown shortcut.
Last but not least, install the following free apps:
ForceDoze
Greenify
Follow the instructions from the ForceDoze app and enable it. It will significantly improve battery life when the phone is idle.
Install Greenify and tap the + symbol to select apps you want to hibernate. The developer suggests that you only hibernate apps YOU RARELY USE. Then occasionally, press the hibernate button and hibernate those apps. You'll see an improvement in battery life. On average I get around 5-6 hours SOT. Sometimes more, sometimes less (depending on usage and apps installed).