Be mindful of apps that are accessing your location in the background. - Keep that to a minimum.
Keep your screen brightnes level or lower. Also be sure your screen is set to turn off after a period of inactivity; if you are of the mind set to forget.
Using only Apple Certified accessories for charging in general is always best.
I see people leave Bluetooth on all the time; only have this on when necessary.
Contrary to belief, closing out background apps doesn't have an affect so don't obsess over that.
Low Power mode can be activated manually before you hit 20% battery level Although certain features will be disabled, it will use only whats necessary.
Keep your battery in good health. Don't let it deplete. 20% at most and even tho it's hard to do at night, once it charges to 100%, unplug it. Try to let it charge completely each time your charge it before unplugging.