Lets Start with a few basic settings.
Display brightness is an important factor in battery life.The more brighter the screen is,the more juice it drains.So keep the brightness under control.Using automated brightness is not adviceable.Try manually adjusting the screen brightness.Using dark wallpapers(on AMOLED display) can help you save some bit of juice.
This is simple stuff,but results in noticeable improvement in battery life.Toggle LTE/3G to 2G while not in use.(While on WiFi).You can use Smart Network
to switch between networks.
For devices that support Fast Dormancy(Read Here
) can disable it to save some juice on 3G.(Link
to disable Fast Dormancy for Xperia Devices)
Even if your wifi is off,the phone searches for signal.To switch off this feature,go to Settings > Wifi > Options(Top right corner) > Advanced >Scanning always available(Off).
Another juice sucker in Android-Location Services
.You can turn it off while not in use.That saves a lot off juice.You can also set the location to 'Device Only" in settings.
Navigate to Settings->Location->Menu->Scanning->Turn off "Wi-Fi Scanning
" and "Bluetooth Scanning
These are the basic stuffs one must look into before complaining about their battery.
Is your battery gauge lying to you?
:Take a look at this
link.This thread explains why you get sudden drain after waking up from sleep.Many people should've noticed that the battery drains faster after keeping the phone idle for some time.It is very informative and is worth a read.