1. Download your rom and Gapps (usually provided on the rom thread)
2. Copy your rom and Gapps to your internal sd card (on your phone)
3. Boot into recovery
4. Wipe Data/Factory, wipe System, wipe dalvik cache
5. Install your rom first, then Gapps
7. Profit !
As long as you stick with CM or other aosp-based roms, you're good to go. You don't need to do fancy things to have a working kitkat rom with root and recovery.
If you want a Stock KitKat rom, then you're going to need IOroot 2.5 to root your G2 and then use AutoRec (provided by cloudyfa) to get a working recovery.
That's it !
Edit: think about updating your recovery beforehand, it won't hurt and may save you from going back to square one