My shih tzu's bark when they are excited. One idea is to tell her shhhh in a calm way and pet her when she is quite. In a very calm voice, tell her what a good girl she is while she is calm. Say no barking when she yaps. Reward her with pets when she is quiet. After a while, she will start to learn that you like her better when she is quiet. Of course, when a visitor comes or something like that, she is going to have her say!