I have recently upgraded a development device to Android 4.3 and given the revised Settings menu spent a few minutes looking for the developer options to no avail.
Fortunately I found this link How to enable hidden developer options on your samsung galaxy S4 and the same instructions work for the S3.
Simply follow these steps:
- Go to Settings → More → About Device
- Scroll down to Build Number
- Tap it repeatedly (It'll show a message telling you how many more times you need to tap it to enable developer mode).
- See the Developer options menu under Settings → More