I have overcome this type of behavior with my yorkie, who is almost 2, but it's not easy. It takes constant watch. I still haven't fully fixed the barking-at-big-dogs problem, but I do know he KNOWS better, and I've found ways to curb the issue (like pick him up and face the other direction so he doesn't see the other dog, haha!) But he doesn't bark/yap every time he sees another dog...just sometimes. I wonder what goes thru their little heads, haha!
Sully used to love ripping apart tissue and underwear. I've partly fixed this by trying to doggie-proof my house as best I can, but on occasion when I did used to find underwear or tissue shredded I'd bring him to it and show him and tell him bad dog. Then he'd get a small time out. When it occured more often, I would put him back into his kennel when he left the house so that he would "earn" his free time again. After a week of not having full reign in the house (not a week of being in the kennel, but a week or so of being in the kennel when we left the house instead of letting him run free). Anyway, after a while I'd give him a chance and he would do better.
It's just a little at a time and also with that, a lot of praise and love for what he's doing right.
