Can anyone tell me anything on shih-tzus?

i just got a new shih-tzu. i am not sure how it is going to act to 3 schnauzers, and a boston terrier. and, or they good with kids? are they good watchdogs? do they obey their owners? can they be tought tricks? do they catchon to tricks easily? man, there are so many questions!!!! so, just tell me everything you know about them. PLEASE HELP!!!!