Recommandations
To save battery:
Don't use 3G network
Don't change CPU freq
Don't use live wallpapers
Use conservative governor if you use your phone for calls only
To play recorded videos:
Use an external player supports Mp4 encoding like MX player
Reboot phone:
After using Wi-Fi tethering (has reboot issue)
Use HWA Settings app:
To disable/enable hardware acceleration for gmail, facebook and other apps (fixes white screen issue)