With my dogs, I did a lot of work to make sure they were well socialized, well exercised and had a lot of obedience training. I can not emphasize the obedience training enough. We did classes and I made sure to have my husband go through the set of commands (once the dogs learned them) as well as my in-laws and strangers we met in the park who were willing to participate. Obedience training builds confidence and structure into their lives.
Mscat - you have children. Once your dog knows the command sit, teach your kids to give her that command with praise when successful and each command thereafter that your Yorkie learns. Your little devil will start treating them with respect. Also, include them in walks.
Find a dog park that has 'small dog' hours. Online there are also tons of meetups. Search them out! Having that outlet was so, so useful. My Yorkie Mix, Ella Bean was a rescue and when we first got her, she was aggressive and MEAN. She would growl and bite.
Aggression stems from fear. Take your dogs with you as much as you can and don't hold them - walk them. Reward them for dealing with a stressful situation with tons of treats and praise.
Also, I love to baby my dogs. I dress them and coo at them and love them to pieces - but I know that too much of that can cause serious behavior issues. But with the rest of the structure that my pups have, we have worked out behavior issues. My once terrifying little Ella is now a sweetheart - but it took time. We have had her since February and only now is she showing her true, sweet personality. She even gives 'high fives' on command!
I am not a professional trainer, but the classes taught me the common sense it took to have well behaved puppers. Remember that the classes exist to teach you how to teach your dog - just going isn't enough. You must practice everything in the classes every day.
It takes a lot of patience, repetition, praise and treats! Keep us up to date on your little devils. Soon, I am sure they'll be angels
