One trick which helped me to save around 1/3rd battery -

get one screen (of 4) without any widgets or whatever - just blank (actually, black is preferable) and keep device on it each time then it is not needed.

This helps saving battery because in my pocket case with magnetic claps it may switch ON a screen in my pocket case (KBD has a magnetic sensor, some bug does exist about this problem) for some time. Even w/out magnetic case it saves energy because on each screen wakeup any widget application on this screen is called and if that application has some Internet data (like Foreca weather) then it communicates via 3G/WiFi each time then device is unlocked.