Wow...it's been a long time since I've been on the BB.
I have a 8 1/2 month male GSD. He has not been neutered yet. I took him to get evaluated by a breeder/trainer. She told me that he is dominant, I already new that, and would have to teach him dog avodiance. He is very friendly with dogs, but she said when he gets older and tries to mount another dog that doesn't want any part of it he will most likely get into a fight.
She had her 4yr female with her that didn't take crap from Gus...which was the first time he ever had a dog snarl and bark at him.
I'm just wondering how you go about teaching him to leave the other dogs alone and to ignore them.

If you want him to never take any interest in other dogs, don't ever let him play with other dogs, and when you meet one, let him look and sniff for a few seconds if you like, then keep walking, reward him for turning his attention back to you, and later correct him if he won't leave the other dog voluntarily.

If you want him to be able to be friendly around other dogs and play with them, but you just don't want him to get in fights, you need to make sure that, especially while he is young, he only has contact with dogs that you know are very friendly. You want to use you obedience comands (especially leave it and come) REALLY OFTEN around other dogs and be serious about them so he will never think it is an option for him to not do what you say around other dogs. This will help him keep himself under control and help reinforce your alpha status too, since he will have to remember that you are in charge even when he is off in dog world. If you see him mounting another dog or exhibiting other aggressive behavior, call him over to you and make him sit at your feet and stay for a while. Time-outs aren't just for children <img src="/ubbthreads/images/graemlins/smile.gif" alt="" /> and when your dog sits at your feet while other dogs play that sends him a very strong message.

A lot of people who are into working or sport dogs will say that there is no need for your dog to socialize with other dogs, and I think that is true, but I personally have pet dogs and I love to watch them play with other dogs and I am glad that they are able to. Dominant temperaments can be managed but you can never turn your back on your dog when he is with any dog you don't know well or any adult male dog. Read Ed's Q&A about dog fights and read up on body language and pack behavior so you can be sure that you are knowledgeable about the risks and how to manage them.