Tail-chasing, in most cases, is simply a sign of playfulness, but keep an eye out if your dog starts doing this excessively. It might mean there’s a health or behavioral issue behind it; for example, if your dog chews at his tail when he catches it, then he might have skin allergies or anal glands that need to be emptied at the vet.
If your dog starts chasing its tail all the time and in an obsessive manner, it may be a sign of OCD. Yes, this affects animals, too. You’re better off checking with your vet, just to be on the safe side.
Yowling
While you may think your dog is trying to yodel, this may be your dog trying to communicate with you. In fact, many owners swear that their dogs can speak to them, even if there is no substantial evidence to back this up.
A writer for an animal journal comments about his dog's yowling: “Our German Shepherd rescue, the sweetest dog we have ever owned (unless you happen to be a cat), is 9. She 'talks' about everything! Grumbles, over being denied a cat lunch, has 5-minute conversations over going out for a walk, exchanges pleasantries (you would swear) over how happy she is to see someone.”
Eating Poop
Yes, dogs can do this from time to time. It is extremely disgusting, but it is not that uncommon. When a dog starts eating its own or other dogs' feces (also called coprophagia), it usually comes down to one of two things; either it is a behavior that can be corrected through training, or it is a sign of malnutrition.
The best thing to do is to take your dog to the vet if it starts doing this too often. If your vet rules out any nutrient deficiency or medical reason, then it's time to go to a trainer to help your dog break the habit.
Licking People
When your pup licks you, it is usually to say "I love you," or to seek out your attention. Also, you can taste pretty good; don't forget we have nutrients and minerals in our skin, and plenty of sodium to boot. We're basically a salty treat to dogs.
If the licking becomes too intense, training your dog to not do this can be done with basic training. The best way to go about this is to ignore your dog when it licks you and reward it with a treat when he stops. Oh and that myth about dogs' saliva being cleaner than humans'? Just a myth.
When Dogs Hump
Humping is a very common and natural behavior in dogs. And contrary to what most people may think, it is not always sexual in nature, or a dominance thing, for that matter. Dogs can hump other dogs, objects, or people, and it is usually a playful activity for them. It does look quite funny, to be fair.
Unless the other dog is bothered by the humping, there's really no harm in them doing this. It's not really a problem unless it bothers the owner, and if the humping is with people, then you might want to break the habit for other people's sake.