Don't know about everyone else, but this is the process I use to return to complete stock, with 0 flash counter and official status, (there are lots of guides though):
1. Backup everything you need, including data from internet SD. It will be wiped!
2. Download latest stock fw from sammobile
3. Flash fw with Odin.
4. Once you get to boot logo, reboot into recovery mode. (Will be stock recovery)
5. Choose 'Wipe data/factory reset'
6. Reboot into download mode
7. Flash 'cf-auto-root' (available in many places), with Odin.
8. Reboot fully into ROM.
9. Install triangle away
10. Use triangle away to reset flash counter.
11. Boot phone, and Select 'Full unroot' from SuperSU app menu.
12. Reboot into recovery and choose 'Wipe Data/factory reset' again.
14. Restore data.
Phone will now be stock, with 0 flash counter, unrooted and official status.
There is probably a quicker way to do this, but for me this is the most thorough.
Sent from my GT-I9300 using Tapatalk
Hit Thanks If I helped
Galaxy S3 (GT-i9300) 16GB
Recovery: Philz Touch Recovery v6
Modem: Whatever works
ROM: Whatever tickles my fancy
Kernel: See above