How do you tell which brake pads/rotors (front or rear) need to be replaced on an A4/B6?

Just so you know, I've replaced brakes/pads/rotors on many different cars. I've built cars. But, I don't see the wear indicator clips that I usually see on other cars.

So, how do you tell which pads need to be replaced?

A picture of any wear indicators would be helpful.

Thanks,

Mike