Default [Q] Rom Backup Advice (i9500)

Sorry, I recently posted this in the wrong section. Mods feel free to move/ erase as you see fit.

I am needing advice with backing up my Cyanogenmod 11 stuff. How do you guys do your backups, enabling you to flash a newer version etc and not lose your data and setup preferences?

I flashed CM11-0303 (and appropriate kernel), then did un update to 0307 and re-flashed the kernel again. This causes major issues and I had to reflash 0303 again from scratch. I was going to only start updating with official CM updates but apparently you can't install an official release update over a nightly install. Is this true?

Thanks, my phone is an S4 i9500. Hope you guys can help because I now want to reflash a new official release without losing my data and setup preferences