I have house trained several puppies and have found this method to be one of the most effective and least frustrating for pup and new owner. First I strongly suggest purchasing a kennel to be your puppies new "den". Your puppy will spend a great deal of his time in the kennel for the first few months. Feed your puppy treats and special chew toys in the kennel. You should always leave your puppy in the kennel while you are away from your home or can not keep a constant watch on the pup.

Structure and a consistent schedule along with a calm matter of fact demeanor are keys. 

First thing your new puppy needs is food and water. You should feed pup twice a day. Always have water available, via water bottle. (available at all pet stores)  

Water bottles are strongly suggested because they keep the face dry and clean. Water bottles also discourage red yeast that will grow in a wet faced Shih Tzu.  

After your pup is finished eating you can either play with pup or put him back in kennel. Mother nature predicts that about 5 to 25 minutes after eating your puppy will have to potty. Tell your pup " Lets go potty" in a sweet encouraging voice. Place pup on ground and say again "go potty". Your pup will not understand this ritual at first, but rest assured that potty will soon arrive. The first week or two is time consuming with this but just walk around out in the yard and wait for your reward. Walking stimulates them to potty. After pup does his business reward him with a very pleasing voice " good girl (boy), go potty outside, good girl!" 

After your puppy potties outside you can take pup inside to play for maybe 30 min at a time and then back in the crate or kennel. If your puppy does not eliminate outside he needs to go back in the kennel for another chance to potty outside in about 30 min. This will be inconvenient at first but your puppy will catch on. Your puppy needs to learn to control their bladder and bowels. By keeping them in a confined area they are detoured from eliminating and encouraged to hold it until they are out again. 

Try to take your puppy to the same place every time. The scent acts like a trigger to make puppy go.

First thing in the morning pick your puppy up out of his or her crate and carry them outside to their potty place.

Inevitably pup will have accidents in the house. I use diapers on all my pups to minimize frustration on my part. But the diaper is not a ticket to allow your pup to run freely in your home. If your pup is allowed to do this they will think it is OK to soil the floor in your home. You must watch your pup at all times that they are out of the kennel. If you see your pup squatting to soil the floor you must act swiftly and scoop pup up, take off diaper and take puppy outside to the potty spot. When your pup finishes his business outside you must reward pup with happy voices saying "Good girl (boy)." Training could possibly take a couple months  or less if you are lucky. Most pups are trained by approximately six months of age. Don't give up on pup, she/he will learn with encouragement and lots of love. Never, ever spank your puppy or yell at him or her for soiling in the house. This only creates negative association with his or her body functions.  Shih Tzu are very intelligent dogs and respond very  well to your voice tones.

I recommend , in the beginning you  take pup out about every hour. If you work during the day you should take pup out for potty as soon as you get home. The more consistent you are the faster your pup will learn. Consistency is your most important asset. This may not happen over night so patience is the key. Keep your pups kennel as clean as you possible can as a cleaner kennel means cleaner habits for pup. 

NOTE: Sometime purchasing a diaper in the beginning creates a "safety" net so accidents go in a diaper and not on the floor. This creates a little less stress during this challenging time. This is not a license to forget potty time.