No one enjoys when a dog is sniffing inappropriately. It can be not only annoying but also embarrassing and sometimes messy if your dog greets you in business attire or nice clothing the same way he welcomes other dogs. This simple greeting from your dog can leave slobber on your clothes. Sniffing while walking can also become distracting and drag out walks, leaving you pulling your dog along rather than enjoying a nice casual walk or a walk which increases your heart rate for exercise. Teaching your dog to stop sniffing, whether it's inappropriate sniffing on people or distracted sniffing everything in his path, is something you're going to want to teach your dog early on so that you can enjoy your time with your dog and have guests over without him putting them in embarrassing situations!
Training your dog to stop sniffing will depend on the situation your dog sniffs most often. If your dog is sniffing anything and everything he comes across while you are walking, you are going to want to do this training on walks. If your dog is sniffing you or other people he greets inappropriately, you're going to need to set up some of these situations to train your dog during an occasion where he sniffs typically. You will also want to teach your dog some basic commands such as ‘sit’ and ‘leave it.’ The ‘leave it’ command can be used for any sniffing to get your dog's attention and tell him to leave whatever it is he has interest in alone.
Training your dog to stop sniffing will require a bit of patience. You can teach any dog to stop sniffing at any age. But you will need some patience and consistency. Be sure to have a leash if you're taking your dog on walks--and some tasty treats to provide your dog to celebrate a job well done. Train basic commands so you can use them during this training.