Also, if you are on a ROM like CM10, AOKP, or any ROM that’s non-Samsung, non-TouchWiz, you will definitely need to do a factory reset. You can also do a factory reset in CWM Recovery BEFORE unrooting, that will not erase the contents of your internal storage (then you can skip the backups).
If you are returning your phone for warranty, run Triangle Away app before unrooting, that will erases any traces of root. (Also installing a stock firmware DOES NOT increase binary count.)
This method is using ODIN and Windows computer. If you have Linux or Mac computer, you can also use Mobile ODIN PRO (on Play Store) to do the same thing.
So, let’s unroot/unbrick your Galaxy Note 2.
Step 1. Turn your Note 2 off, then hold down Volume Down, Center Home, and Power buttons together to enter ODIN Download mode warning screen.