[Samsung Galaxy Grand Quattro] Axit Mehta:
I made a lot of experiments trying to squeeze most of my GT-I8552 battery & RAM, and finally I reached those results by the below strategy (please note that this will be just strategy/tips, not detailed steps), and on ROOTED STOCK ROM It currently gives me:

1) Average Screen Off Discharging Speed 0.3-0.5%\hour (so battery needs 200 hours to discharge, or more than a week!)

2) Average Screen On Discharging Speed Between 10%-20%\hour (no Gaming) (so working hours about 8-7 hours)

3) Free RAM after full startup 65%.

(I gathered those statistics by setting Tasker to calculate them for me).

Battery Tips:

So to see almost a perfectly horizontal line of your battery discharge during your sleeping, you will need:

1) Rooted Stock ROM (I tried this on KitKat latest version).

2) Greenify.

3) Tasker

4) Your brain :p and some work.

OK to get most of the battery, do the following:

Remove all LG & Google Bloat ware; search XDA how to do that.

Disable all animations in you Settings-> Accessibility, this will save our battery and make apps faster.

Now all of the work should be done in Tasker, I assume that you already know how to work in this thing, if not search XDA there is a lot of tutorials...

Once your screen is off, do the following in Tasker:

Turn off the following : WIFI, Bluetooth, GPS, Auto Sync.

Greenify all bad behaving apps, after that use tasker to force close many of the bad behaved one (you should experiment with this).

Down Clock your CPU, for some reason my device reboots unless I set Governor to conservative or onDeman, so here we put it on conservative, with CPU clock between 300 and 652 MHz, there is no need to make it lower, because it gives no better battery life, and it makes wake up time longer.

Those steps are enough to make sure that you will lose about 0.5% per hour only! (my CPU needs about 5-10 minutes to enter deepsleep, this means that your battery drain during this time will more than 0.5%)

On screen ON, you need to immediately set back your CPU to onDemand mode, otherwise it will lag, actually I made 3 profiles for CPU, low (during screen of), medium (when screen on), and high (during gaming), so here I set the OnDemand with frequency 300-1190 MHz, and you will not notice any lag with those settings, also you need to set the maximum priority for the Tasker profile that will do this, well actually I made my own Lock Screen by Tasker screen so that tasker will stay foreground app and has best CPU priority, so swapping CPU profiles will be quite fast and you will see no Lag.

Also I set a periodic sync, when screen off each hour my phone wake ups and turning on wifi (or 3G if I’m out) and turning on AutoSync for couple minutes, and then turn all those things again to enter DeepSleep (step 1).

you need to make a good Screen brightness management in Tasker, there is tutorials on line for that.

Finally, during working, I set many specialized profiles for different apps I use a lot, for example, you don't need AutoSync when you are talking by phone, or reading a book, also when reading books, you don't need high CPU frequency, so I lowering it down, all this tweaks needs some work, but anyway you it will give you considerable battery gain, and you will see that the application that you really using a lot are not more than 10 apps.

I would like to note that I tried many ways to optimize this (except trying different ROMs) like playing with application's wake locks, but nothing worked as good as this strategy for me, if you have some more suggestions it will be great.

RAM Tips:

Many of us trying to make our phones customized and more beautiful, but after a lot of tries I found that all those things only making things worse, even for a monster like LG G2: I tried almost 99% of Launchers available on store, and all of them are very bad in scene of resource usage, for example the most beloved Go Launcher, having 200+ apps, and 3 pages of widgets, uses about 150 Mb. of RAM, this is too much, considering that android itself using about 200Mb. in worst scenarios, even the launchers that claims to be very efficient like Lightning & ssLauncher, that is not true, because once you install them, they indeed use too little at the beginning, but once you customize them and will add widgets, objects to them, they will jump up to 100Mb., well this still is better anyway than Go Launcher.

So to be short, the best one in terms of memory usage, is definitely, and without any competition, is Smart Launcher, it seems that it has a unique possibility to draw/load the widgets on demand (you can add them on special pages) and once you go back to main screen, it will free up used memory in minutes, that's really great, because this launcher on average uses only 50Mb. whatever the widgets you use!!

Also I would like to note that most Lock screens are very memory hungry, I tried lot of them, and none of them used less than 40Mb.!! so it almost like a second launcher! even the best of them like widget Locker or C-Locker! that why I made my own by Tasker itself, but note that after designing a scene in Tasker, it will use a lot of memory (70-80Mb.), and for some reason doesn’t free it unless you restart Tasker, and fortunately after that it will use not more than 20-30Mb. even when the scene is visible! so considering other things Tasker is doing, it's pretty low! so I highly recommend this.

Also any programs like recent app's viewers, side bars, screen buttons etc.. are also very memory hungry, I tried a lot and none of them really efficient, don't dream to get one with less of 50Mb. usage! so it's better, in my tests, "on screen buttons" are the best one with about 10-15 Mb. usage in case you don't like the navigation bar as me))