Great question. Timber will meet and greet other dogs. But then as they or we turn around to leave he starts that annoying "Yap, yap, yap, yap". Im not sure what it means. Maybe like "come back, I wanna play". I dont know. But a lot of other dogs find it irritating too.
I took Timber by the vet today to check his weight. (he gained ten pounds in 3 weeks!!!!) and there was a female GSD there. I talked to the owner outside my SUV but then opend the back so that she could meet Timber. Timber was in his crate. She jumped up to say hi and body language was friendly. But as soon as Timber started that yapping, she started getting nippie and growly. I did tell Timber Hush and No bark. But he wasnt listening.
This yapping is also something Timber does at puppy class. He couldnt stand it when the other people were taking their dogs through the tunnel. Yap, yap, yap was all anyone heard. Thank God we all like dogs.

My trainer told me that to teach the dog "no bark".....as soon as they start barking spray Binaca mouth spray in their mouth. She said NOT as a punishment but as a result of his barking. She was like "okay you barked, I guess you want some mouth spray". It seemed to work at class but I havent bought any for at home.
Good luck...cant wait to hear other replies.