Shih tzus are usually among the easier dogs to housebreak, however, most people find themselves torn between using a crate to train a dog and some of the more creative methods that people have designed. Regardless of the method you choose, always remember that the goal is to stop all elimination in your house and make the process as painless as possible for everyone involved.
For starters, punitive methods of punishment are now seen for what they are: mild forms of animal abuse. There is no reason to shout or beat a dog, certainly not a shih tzu. Simply teaching your dog what to do and letting them know when you're displeased, you can come to an understanding that is mostly based on reward, whether that be treats or your affection.
The shih tzu is such an affectionate dog, praise usually does the trick. If you choose to let your new shih tzu puppy have the run of the house, at least restrict it to where you can keep an eye on them. This, however, only works if someone is always around to let the dog out, as is often the case with freelancers.
Most people who have to go to work during the day ultimately resign to confining the dog to a crate, or in some cases, teaching it to use the toilet. Honestly, this can be taught, but with a lot of patience, encouragement and rewards.
Remember that there is no point in scolding a dog after it is done committing a foul misdead. If you can catch them in the act, you can voice your displeasure, but otherwise, don't bother - they've already forgotten what they were just doing. Puppies have a hard time remembering anything they haven't done a thousand times before, but when an idea sticks, it does so for good.
Too much shouting when a dog is young and not being responsive enough lead to difficulties with toilet training. No matter what, you need to be very diligent about helping your dog get things right as well as never letting them get away with unacceptable behaviour. As soon as a shih tzu thinks there are exceptions to your rules, you've just lost credibility as a leader.
The principal on which the crate works is that a dog won't eliminate where they sleep - certainly not if they can't just move over to get out of the way. They may be animals, but they don't want to lie in their own waste. By making the crate a relatively comfortable place, with soft bedding, food and water, a crate can be a place that your dog feels safe in.
Crates also have the added appeal of keeping your dog from getting into the kind of mischief that does make you want to scream. If you're going to be around all the time and can be consistent, it may not be necessary, but most people at least start with a crate, even if they grant more freedom later.