A lot of it is genes, that's why you should ask to see the parents. I didn't know that when we got Loki. I knew you should ask to see mom and dad, but I thought it was for looks and size, not temperament. Now I know that. I also now know why pups should stay with mom and dad and siblings until 12 weeks, so they learn "manners". We got Loki after 12 weeks, but mom was not there and neither were litter mates. Even though we got him into classes right away and he has continued classes since (he's 2) we still have trouble with him, but it's manageable. He is a brat around big dogs and he's kind of possessive. But, through working with our trainer we have made a TON of progress. Some of his problem is temperament and some is fear/reactivity. We try to be very consistent and give him IMMEDIATE time outs if he acts up. He only gets attention when he is good or does what we ask. I don't think our trainer will ever understand how much she has helped us. Without her I would have a complete monster on my hands. Instead he is only about 5% monster
It's not necessary to revert to "old school" obedience. We use positive training (same as clicker). The problem with the old school punishment methods is actually 2 main things. First, a dog who is already fearful will become more fearful. Second, unless you are an expert/professional you won't have the timing to do the corrections. You'll end up punishing the dog for the wrong thing. And in addition to that, to do a correction you truly have to HURT the dog. The idea with old school corrections is you only have to do them once or twice because you hurt the dog and they won't do it again. Trust me, you really don't want to hurt your dog. You can potentially make the problem WORSE because now they are even more afraid and/or their fear is justified. As in - Birds are scary so he barks at them. (Leash Pop) OUCH! OK birds really are scary, when he sees them he feels pain.
Positive training is good for us because it helps us communicate. Loki would snap at us when we picked him up while he was lying down. Not only did the trainer give me some common sense advice like - would YOU like to be picked up while sleeping? But also had me teach him a "move" command so I just ask him to move over on the couch rather than just picking him up and moving him. He is always happy to move, especially when he gets a treat sometimes for doing what I told him!