How to get OEM USB driver for Samsung Galaxy SIII with model number GT-I9300

I had the same problem following the same tutorial. I'm using Eclipse IDE, on a 64-bit Windows machine. This is how I solved it:

1. Theoretically, the USB driver for a clone version should be the same as a regular one, hence I´ve downloaded a similar model.
2. I had to configure a few environment variables to make ADB work (tutorial).
3. Made the regular procedure: 'adb kill-server' and 'adb start-server'.
4. And finally, the most important one, while Eclipse IDE was open, I restarted the debug mode on my phone (just deselect an select again the option). In this step, on my phone, it asked me to confirm the connection!

I hope it works for you too. Sometimes the driver step might be skipped since Windows installed it automatically. I unistalled it and reinstalled several times.