1 – Switch your screen to a black background.
2 – After you have used the Greenify app mentioned above to hibernate all the non-essential apps that you can think of, find out which remaining apps are using the most “juice” and completely disable them if you don’t use them on a regular basis.
Just tap Settings>About Phone>Battery>Battery Usage for a list of running apps that are consuming power. They will be listed top to bottom in order of their power usage.
3 – Either put your phone into Airplane Mode or turn it off completely when you know you’ll be in an area with an extremely weak cellular signal (especially if there’s no signal at all).
The constant search for a signal will run your battery dry faster than you can say your ABC’s (well, faster than you can recite the Gettysburg Address from memory anyway).
4 – Keep a fully-charged portable battery pack on hand for recharging your phone’s battery when you can’t use a wall charger or car charger to charge it back up.