Bowing
When your dog lifts up its rear end, bows its head to the ground, and wags his tail vigorously, it means that he wants to play with you, right now. This can also be done at times when the dog wants to play with another dog or animal. It is not threatening in any way, and should be responded to immediately if at all possible.
Rolling Over
Dogs roll over on the ground because they know who is in charge, and they are trying to display that knowledge. They may roll on the ground when they have done something wrong you may not know about yet, or they might roll around on the ground because they don’t want to follow a command. However, it can also be as simple as meaning that the dog wants his or her belly scratched.
Tail Wagging
Tail wagging is to dogs as smiles are to humans. Most often it means happiness, but it can mean other things as well. It could signify nervousness or irritation at a situation. A wagging tail that is low almost certainly signifies this. You can usually tell why the dog is wagging their tail by what is going on around them, such as master coming home.
Mounting
When a dog mounts another dog they are showing their dominance over that dog be it male or female and this is a possible trait that you may come across.
Humping
An extension of mounting, this sexual behaviour can be exhibited by male or female dogs... even neutered females. It can happen as a show of dominance, a desire for sexual gratification, a show of happiness or nervousness. You can stop this unwanted behaviour by making a loud noise or some other distraction for the pet.
Yawning
Yawning in dogs usually means the same thing it means in humans. The dog is either tired or stressed out. In the case of stress, the yawn may come on before an incident or just after it has been defused.
Tongue Flicking
Dogs generally flick their tongues when they are feeling uneasy or apprehensive. This may be combined with yawning. It means that the dog is nor comfortable in some way, or is in anticipation of something great like a long walk.
Tail Tucked and Ears Back
When a dog is feeling really uncertain he will tuck his tail behind him and push his ears back, as well as take a few steps backward. Consider what or who has entered the room since the dog acted this way, and slowly introduce that person or thing to the dog. Overnight visits from strangers to the dog may not be a good idea if they are uncertain about that person.
Nose Nudging
Nose nudging is your dog’s way of getting your attention. It could mean the dog wants to be walked, fed, or played with. Whichever the case may be, it needs your attention. Use deductive reasoning to figure out what type of attention he or she needs at the moment.
Paw Lifting
This often means the same thing as nose nudging. This is also an attention seeking behaviour, but one that should be awarded with attention if the opportunity presents itself.