Screen brightness, mine is down to 14% works perfectly, this is a big culprit in draining mobile devices battery's. I disable sync'ing with things like Google services, in the apps settings section, remove or disable unwanted apps, in the Network/data settings put apps I don't want on restriction so they can't use data in the background and also limit or kill off any frivilous wifi-scanning and roaming possible. When it comes to apps, I believe fewer is better, many of them like task-managers, monitoring, battery savers etc think actually just end up draining someone's battery faster. They may kill off apps, which then just turn around and reload anyway and for something like CCleaner which I was fond of it when I was using Windows, it's a disk cleaning deal, noticed it was using 60avg-100@times-mbs of memory and that's ridiculous for something I don't need to do very often.
Can just install/use and remove it occasionally and well behaved apps such as browsers already have settings to clear caches/cookies/history etc. Firefox mobile does a mobile browser I like named Lightning does too. I use Lightning majority of the time for web browsing in Android. Really light ( in terms of sys overhead and bandwidth) and fast, plenty of features and user friendly too.)When comes to mobile browsers, I do tend to leave javascript disabled, block images when appropriate to save data and boost speed, block tracking and disallow 3rd party cookies. I turn off frivilous vibrations/sounds in Android, of course that's just a preference. Don't need a buzz/vibe or ding sound every time I push a button ... dialing a phone number. That little motor that cause the device to vibrate takes a tad of juice to work. I also set a pitch black home screen and app-drawer wallpaper, which doesn't do anything for battery on LCD phones, I just like the look, a hangover from #!(Crunchbang gnu/Linux)days but it does on devices with emoled screens. It's also said and makes sense that minimizing home screen widgets is good juju for conserving battery juice in Android. I also tend towards keeping as few screens on home screen as possible (ideally only one) vs having a ton of the things.
The big reason for posting on this though, enabling Developer Options is really, really cool. You trackdown in settings (found in About Phone) where it shows the version of Android running on the device, tap that 7 times in rapid succession and it'll add a new settings category for "Developer Options" to your device. Doing so provides quite a few new settings to tune/tweak and these are some of those I like the most. It let's me choose a default action for when a usb is plugged, ie: I chose MTP File transfer, whereas on my phone this is something I'd have to set/choose every time and was annoying. Provides some cool tools for looking at Memory usage, running and cached processes, what's included in it could actually replace a stand-alone app someone may be using for the purpose.
Of course not all apps are created equal, some are bound to be better behaved, allowing for them to be easily disabled between uses, using less resources for the same function/features, whether it be keyboard, default launcher ... whatever else. Something else I like about developer options settings, you can disable or turn down animations, window animation scale, transition animation scale and Animator duration scale. I choose to disable all of them and the device is faster as a result. Don't have a bunch of animations I don't care about popping up in windows, home screen or start/shutdowns. There's another where someone can limit the number of background processes, can set it so only 4 max are allowed. The phone was noticeably snappier after setting this to only 4 but didn't want it to be a situation as described above, where processes are getting snuffed, only to turn around and start again, resulting in a viscious battery draining cycle, also don't want to risk adversely affecting the basic functions of the device, ie: A phone, it's good to be sure it will ring and receive incoming calls, unless explicitly set otherwise.
There's a bunch of interesting settings to play around with in Developer Options. One which will allow the bootloader to be fiddled with, oddly on this carrier locked phone, Developers options tells me the bootloader on it is already unlocked. Some can no doubt cause a person headaches and hassles but shouldn't be anything not easily reversed regardless exercising a tiny tad of common sense. After tuning as described, removing apps like CCleaner other task managers type appage, optimizers etc which were just hogging device resources and draining my battery for little benefit, I freed up 120mbs-ram or more. After this general Android dorkage in total also doubled my screen time (when you're actually doing something like browsing etc) as relates to battery drain, used to drain at a rate of 20% per hour of screen time, now it's at or around only using 10%. This is a non-rooted device and I don't feel like bothering to root it. Phone is running much lighter, battery charge lasts much longer and device has smoothier and speedier performance for not much effort invested.
Android is hella-cool and keep meaning to mess with it to greater extent. That lil thing in your hand can do practically anything/everything any other computer form factors can handle nowadays. It's ridiculous, amazing stuff. Gradually trying to move more into the area and see what all really awesome junk someone can do with a mobile device. Did install an FTP server on Android, so I can transfer files to/from via wifi on the thing with sftp or SSH without need of bothering with usb cords. Haven't bothered fully getting it setup as of yet. If someone would like to share some of their Android tips, tricks, appage they've found that works really well. Etc and so forth, by all means do.
Get ya mind outta the gutter people, we're discussing Android! Sheesh. 