There's a lot of tips for saving battery on your phone but one of the main things is disabling stock apps you dont need on your android device. If you're not able to uninstall those, deactivate them via the 'apps' menu. This includes the proprietary google stuff.
One more thing is enabling the developers options and set the three animation scaling options to 0.5.
Then check your phone specs. In case you got an OLED display, set your lock and home screen wallpaper to a black picture and use a black menu theme. Using OLED technology the black pixels don't have backlight enabled which means that you actually use maybe 30% of the energy showing a light text on a black background instead of showing dark text on light background. In case you have an LCD display all of this doesn't matter.