The front LED can be disabled by going to Settings -> Advanced Settings -> Button Backlight Brightness and set it to 0.
Saving battery is pretty simple. You can use Greenify to kill apps running in background and save RAM and battery. Turn off data when not in use, lower screen brightness are some of the things you can do as well.
Microsoft Certified Professional
Sony Ericsson Xperia Arc S(LT18i) - Unlocked BL(CM11) -> INO 2(4.2.2)
Sony PS VITA PCHJ10001(初音ミク Project Diva F Limited Edition)
1.69 - > 1.80 - > 1.81 - > 2.00 - > 2.02 - > 2.11 - > 2.12 -> 2.61 -> 3.00 -> 3.01
Sony PSP - 2006(Original replaced with 2001 MOBO)
3.60 OFW - > 5.00 M33 -> 5.50 Gen D3 -> 6.60 PRO C