People have been using whistling to control their dogs for more centuries than you can imagine. Long before the days of the factory-made tin whistle, they made whistles from wood or bone. A great many simply used their mouth to create a range of whistle sounds, giving their dogs commands they might not be able to hear otherwise. Shepherds still use a flat whistle tucked in their mouths to create unique sounds that tell their dogs which way to go.
However, no dog instinctively knows how to respond to commands given in this manner any more than they know how to respond to voice commands without being trained to do so. You can start this training from a very early age. In fact, the sooner you start training your pup, the easier it will be for you to train him to respond.
The idea here is to train your dog to perform a number of commands in response to specific whistle commands. By the time you are done, your pup should be able to perform all basic commands such as 'come', 'sit', 'stay', 'down', and any others you want, using nothing more than carefully thought out whistle commands. One thing to keep in mind is that once you have developed a series of commands, be sure to stick to them. Changing them in midstream will only confuse your pup and make training almost impossible.
You do have a choice when it comes to what type of whistle to buy. Traditionally, a very loud whistle is used. But you can also work with a "silent" whistle that only your dog can hear. The funny thing about the silent whistle is that, in many cases, they are easier for your dog to hear than the one you can both hear.
The best time to whistle train your pup is at the same time you are teaching him the basic commands. This way he learns both the verbal and whistle commands at the same time. Of course, you can train any dog to follow whistle commands, it just takes a different approach and a little more time. There really isn’t much you need in the way of training supplies, but you will need:
Before you start working on command training, use the whistle in the house to get your dog used to hearing it. Then try giving a few blasts, if your pup comes over to you, give him a treat. You don't need to do this too often, just enough for him to get used to the sound and to responding to it. Remember, you need to pre-plan your whistle commands, consider using a single long blast for 'sit', four short blasts for 'come', and if you really want to get fancy, two short blasts for 'turn left' and three for 'turn' right.