Android Geeks has made a quite good guide on how to install CyanogenMod 11 Nightly Build from scratch on your Samsung Galaxy S3 4G (GT-i9305). Check it out below.
CyanogenMod (pronounced sigh-AN-oh-jen-mod), is a customized, aftermarket firmware distribution for several Android devices. It’s based on the Android Open Source Project, CyanogenMod is designed to increase performance and reliability over Android-based ROMs released by vendors and carriers. CyanogenMod also offers a variety of features & enhancements that are not currently found in these versions of Android. See more posts tagged CyanogenMod. ↩