Your dog doesn't have to have a job to benefit from whistle training. Traditionally the domain of herding and gun dogs, training a dog to respond to a whistled command is useful to you and your dog. Learning how to use a dog whistle takes time and patience, as well as the right whistle.
Dog whistles come in a range of frequencies, meaning they vary in how well you and your dog hear them. Whistles can be plastic or metal and contain a pea or be pealess. A pea is a small cork ball inside the whistle that allows the user to make different sound combinations, including a trilling noise, however the pea can freeze in very cold temperatures. Pealess whistles don't freeze and are better at emitting fast blasts of sound. Dual tone whistles are two whistles in one -- the pea and pealess whistle -- and mega horns have megaphones around them to increase the volume and funnel the sound a greater distance to the dog.
Speak Before You Whistle
After you've chosen your whistle, the next step is to train your dog. If your dog hasn't been trained to respond to your voice commands, he won't be able to respond to a whistle since there's nothing to associate the whistle with. He'll need to learn the recall command of "here" or "come" as well as "sit." When your dog has mastered those two actions at your prompting, you're ready to add a whistle into the mix.
Each command should have a distinct whistle prompt. For example, "sit" may be two quick blasts while "here" is one drawn out whistle. The key is to choose signals that aren't easily confused and apply them consistently over the course of training.
Whistling to Sit
Start with the "sit" command and get your dog to sit properly from a verbal command or hand signal. The next "sit" should be accompanied by the whistle, followed by great praise, and perhaps a treat, for doing as instructed. Repeat several times before attempting to direct him with the whistle. If he responds properly, praise and reward him and if not, give him the verbal command, followed by the whistle. When he responds to the whistle prompt, begin transitioning to the whistle by alternating between a verbal command with the whistle and the whistle only. After he understands the whistle command for "sit," gradually increase your distance from him over multiple training sessions until he'll sit to a whistle command as far as 50 yards away. Beyond that point, you'll be able to train him to sit when he can't see you but can hear your whistle.
Whistling to Recall
A whistle is especially helpful to call your dog over great distances. Whenever your dog responds properly to a "here" command, it should be like a party -- even if he's been misbehaving. Punishing a dog who comes when called will make him avoid you. As with the "sit" command, practice adding your chosen whistle signal to the "here" command, starting from several feet away. As he begins to make the association of "here" and your signal, gradually increase the distance between you. When you work on this command, make sure you always start with a "sit." Since you need to reinforce "sit" as well, you'll want to mix it up a bit. Sometimes you'll whistle a sit and walk away to leave him sit, while other times you'll walk away and give him the corresponding signal to come. Your dog needs to learn that "sit" isn't always followed by a "here" command.
Before You Whistle
Dog whistles come in a range of frequencies and volumes that can be shrill or startling for human ears; take care of when and where you blast your dog whistle. Those loud whistles are effective for carrying long distances your voice isn't able to reach. As well, an especially powerful whistle may be too irritating for your pup's ears. Exercise caution if your dog is especially sensitive to sounds. Consider keeping your whistle on a lanyard around your neck so it's handy. If you lose your whistle, you may have to re-train your dog if the replacement whistle doesn't reach the same frequency of the original whistle, so you may want to keep a duplicate on hand. Finally, whistles are for training, not for stopping behavior, such as nuisance barking or aggressive behavior. Talk to your vet or a professional trainer if there are specific behavioral concerns with your dog.