Its very simple, assuming your NOT rooted, set up Automated Hibernation (4.1+) under experimental features. Then hit the + button at the bottom of the main screen. then select show more apps in the next screen.
After that select any app that you don't need to do its work automatically. For example, DO NOT select things like clock (your alarms won't work) or SMS (you won't get text messages). DO select games, and other programs that you only need when YOU select them and run them. They will work 100% the same for you, you won't notice any difference. They just won't run in the background. They are still in memory, and still load just as fast, and can be selected from the recent apps menu, left minimized (if they are multiwindow compatible). You would be amazed at the junk running in the background. I leave weather apps (so I can get severe weather alerts),and the calendar, and Textra (sms), Yahoo messenger, skype, hangouts and a very few others running. Everything else goes to nap. You need the apps to work when YOU tell them to, and greenify allows that easily. (You know how people say that the number of apps you have on your phone effects your battery life... greenify basically solves that problem, after all why should a game I only play once a week be eating a single second off my battery when I am not using it?)
Depending on how much I install on my phone, I recheck it once in a while to see if I need to add more to the hibernation list. Otherwise its nearly invisible.
The one short coming of being non-rooted, is that often, when I unlock my device, I have a screen showing sometimes with the app info that it stopped, rather than the home screen. A single press of the home button takes me right to my home screen. So no big deal.
Also, I have never used a device that was so stable. I can't remember the last time I had a unresponsive program that crashed. I reboot the phone every 3 or 4 days, mostly out of habit. Otherwise its rock solid.
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