I don't pet an unknown dog on the head. I think petting side or chest is less invasive than reaching over the dog to pet its' head. That being said, I pet my own dog anywhere I want. I am fostering a very large GSD. He is the most affectionate boy. I put him on his side and he lets me kiss all over his face.
Natty Boh 6-27-12
Annie 1998 - 8-2-12 RIP