Dogs are, hands down, the best companions you'll ever meet.
They are loving, they are always trying to get their owner's approval, and they are always there for you! However, some dogs may seem aggressive.
Usually this is because of a few simple mistakes made by their owners.
The most common mistake I've seen is hitting or spanking your pet.
Most dogs are truly trying to do their best for their owner, but when they get hit or yelled at, fear is instilled in the animal and they turn aggressive.
It is teaching a bad habit...
that fear and violence are good ways to express emotion.
Never, ever hit your dog, or you will quickly realize the dog will become out of control.
Secondly, encouraging rough playing like tug of war or something along those lines is very aggressive in nature.
By teaching that this behavior is OK, you are sending the message that this behavior is OK and it will confuse the dog.
They just can't recognize the difference between good aggressive behavior and bad.
Instead, play frisbee or run with your dog.
Play catch, or just go for a walk.
The dog must burn off energy, but make it in a playful, synergistic manner.
Don't play any games which may be construed as violent or confrontational in any way.
Lastly, keeping a dog caged for an extended period of time is never the best of ideas.
Even though you will have to keep the dog caged for at little bit here and there, try to keep it down to a minimum.
Your dog will thank you for it in spades.