There are times, alas, when dogs do not seem like our best friends. At times, they can be downright scary. There isn't much you can do about other people's dogs (except avoid them if they are likely to snap at you!), but what do you do if your own dog is the one causing problems?
Aggression is the most serious problem faced by dog owners. It can take many forms. Your dog may have a problem with other dogs, with children or with just certain people or in certain environments. So, first of all, you should narrow it down and pinpoint the exact issue.
The first step to take is to have a veterinarian you trust examine your dog, to make sure there is not a physical problem that is the cause of disruptive behavior. You should also try to control your dog's environment as much as possible, avoiding whatever tends to provoke problematic behavior.
In other words, do not tempt fate. If your dog tends to fight with other dogs, until you can get a handle on the situation, you really need to isolate your dog from other dogs. The same, of course, is true for dogs who are aggressive towards people. If necessary, use a muzzle. Be sure to warn people not to approach a potentially dangerous dog. You do not want to deal with lawsuits, or other repercussions of your dog attacking someone, whether human or another animal.
Most cases of aggression in dogs can be successfully dealt with. In rare cases, as when you have a young child at home, or if the dog is, for whatever reason, unresponsive to any kind of corrections, dog and owner must part ways. Fortunately, these situations are not the norm. The first thing you should make sure of is that your dog gets sufficient exercise. Aggressive dogs often have too much energy because they are idle.
When exercising or playing with your dog, do not encourage aggression. For example, if your dog tends to growl and snap at people, you should not play a rough game of tug-of-war with a leather toy. This is actually teaching the dog to bite and growl.
Another factor to consider is socialization. Dogs who are left alone for long periods, especially in uncomfortable situations (e.g. tied to a stake or tree or in a small pen) often develop behavioral problems. Dogs are social animals and are not happy being left alone for long periods. If you are away from home a lot, perhaps you can make arrangements to have someone else watch your dog for part of the time.
The above are basic suggestions and will not be enough to correct a serious behavioral problem. The truth is, an aggressive dog needs some serious attention. You will have to hire a qualified dog trainer to help, or take the time to work on your dog on your own, which will take some time, patience and education.
The issue of an aggressive dog is serious and cannot be overlooked. Fortunately, most dogs can be cured of aggression and almost any other behavioral problem. Some dogs, just like some humans, need extra help in getting past whatever problems they may have acquired.