I want to make sure my tiny Shih Tzu is a girl, as some people say its a boy. How can I check?

For a puppy, follow the information in the guide above. If the dog is adult things get a lot easier. Boys have some distinctive habits and anatomy, which should make it fairly obvious if he's male. Slide your hands between the dog's back legs and feel for the presence of two testicles in a scrotum. Does the dog cock his leg to urinate, as this is something female dogs don't do. Where is the location of the orifice from which he passes urine? For a boy (even a neutered male) this is the penis which is located underneath on his belly, whilst for the girls it is between the back legs.