Instead of WHAT is my dog doing, ask yourself WHY.
All dogs have a reason behind every action; we need to know why before we tackle how to go about it.
Anytime you approach a dog trainer and they ask you what you would like to change with your dog, they are not expecting a simple answer. Expect your trainer to ask you a ton more questions, or ask what the context you see the behaviour happen in. This is the most important information to know before putting any training tactics into play.
A lot can change in a trainers approach to a problematic behaviour, in the context of that behaviour alone. Take some time and watch your dog, before, and after they do the behaviour you find displeasing. Notice the patters in their actions. Once you notice the pattern try to distinguish the cause of the behaviour. It is the difference between a dog biting from aggression (that seems to be a lot of peoples default), to resource guarding, to playing, to teething, to simply them being fearful. Like any living breathing creature with a brain, dogs do things for specific reasons. Yes, their actions are not so thought out or calculated like humans, but that's also why there are no "bad dogs" in the world, just miss-understood ones. Once we understand the reason behind a dogs behaviour, we can take the proper steps towards addressing them in a helpful, healthy way.
A lot of what I know about this is from an animal behaviouralist and scientist named Temple Grandin. She is brilliant, and brave, and honestly one of my heroes. If you don't know who she is, you should look her up. Anyways, before I get too off topic, the reason I bring her up is because one of her main focus' in her studies is the idea that all behaviour stems from an emotion (The Blue Ribbon Emotions which I'll probably write another post about).
All this to say, there are reasons behind an animals behaviour, most times because of a need that is not being met in them. Dog's sniff, chase, and bite to hunt. They gnaw and yawn to relieve stress. They bark to communicate. All of these things that owners will come to me asking to "fix" in their dogs, are just natural, normal dog behaviours. It's all about putting them into the right context, and creating structure for your dog to follow. Saying "you can do that, but only when I say it's okay to" is far more beneficial to an animal than trying to force them out of a natural behaviour that they have been bred to do.
This is why it is so important to do your research before getting your dog. Research the breed, and the parents, and the exercises that you will be doing with them in order to fulfill their needs. If it doesn't match your lifestyle, or you are not willing or able to make space for their needs, change the breed of dog to get. If you've already got the dog, make space. You can't take the run out of a boarder collie just because you don't have a backyard, at least not in a healthy way. But have no fear, there are things we can do! Just be prepared to work just as hard as your dog is willing to.