The following is partially information from seminars I've given to parents and children about dog safety. The rest of it is more adult-oriented and sort of off the top of my head.

Dog bites actually aren't responsible for very many deaths in the United States annually. In fact, more people died in 1997 after having been stricken by lightning than after being bitten by a dog. Stillinall, dog bites are scary, and the vast majority of the time, they're also preventable.

-- Do not approach a dog that is "tied out." More than half of the dog bite cases in the United States in 1997 involved tied dogs. If you have a dog, don't tie him up outside and leave him unsupervised! All dogs (and humans, for that matter,) are equipped with a defense mechanism called the 'Fight or flight reflex.' Basically, it means that when faced with a threatening situation, a dog's first reaction is to flee. If his option for flight has been removed (as by a chain connected to a tree or a post,) his only alternative for self-defense is fighting. Tied dogs experience a behavioral phenomenon called "hyper-vigilance." They become acutely aware of the fact that they cannot run away, and that they are vulnerable in that anyone/thing that chooses to can approach them as closely as they please. Tying a dog outside is a dangerous practice. Approaching a tied dog you don't know extremely well can get you hurt.

-- Do not pet a strange dog unless you have been granted permission to do so by its handler. Even normally friendly dogs can react unpredictably when approached, especially head-on, by a stranger with his or her hand extended toward the dog's head. Additionally, some dogs are quite protective of their people, and they may interpret a stranger's approach as a threat to their "pack."

-- Remember that there are only two common causes of aggression: fear, and protectiveness. If a dog is snarling and lunging because he is afraid you will harm him or threaten his territory, belongings, or pack, you are likely to get bitten if you don't figure out what you're doing that's causing him to react and knock it off. There are several ways to communicate to a dog that your intentions are innocent:
1) Avert your eyes! Even though it's terrifying to take your eyes off something that's scaring you, direct eye contact is frequently considered threatening by dogs. Look away, cast your glance down and to the side, or close your eyes altogether. This also happens to be one of the ways dogs defer to each other in nature.
2) Change your body position. An approach from the side while facing the same direction a dog is facing is the least threatening. Don't walk up to a strange dog head-on if you can avoid it. Walking away is another option.
3) Keep your hands down. Approaching a dog with your hand raised, even to pet his head, can be misinterpreted as a "strike-ready" posture. This especially freaks out dogs who are corporally disciplined by their people.
4) Check your tone of voice. Excessively high-pitched, loud squeakiness ("oooh, who's a good doggie nice doogie CUTE doggie!") can be as frightening to an anxious dog as hollering and screaming. If you must speak at all, use few, simple words, and talk slowly, softly, and in a low tone.

-- Understand a dog's body language. There are a few things to watch for that many behaviorists consider "telltale" signs of a pending bite, or bite attempt. Can you see the whites of the dog's eyes all the way, or almost all the way around the iris? If yes, back off. Are his pupils entirely or almost entirely dilated? If yes, again, be careful. A dog's eyes (and guess what, a human's too...) open wider and the pupils dilate whenever a particularly emotional thing is happening. The sympathetic nervous system causes these and other reactions in order to allow the most sensory information possible into the dog's brain. What are the dogs ears doing? If they're folded closed and flat against his head, he probably means business and again, you should tread lightly. Where is his tail? Tucked far between his legs and onto his belly? That is a signal of fear. Held WAY up high over his back? Sometimes (ONLY sometimes,) that is a signal of dominance and/or protectiveness. Note: A wagging tail is not necessarily a sure sign of a friendly dog. Is the dog baring his front teeth? Is he growling? These are more obvious indicators of a potentially aggressive dog. Also, check out the hair on the back of the dog's neck and down his spine. If it is standing on end, once again, you may be dealing with a fearful or protective dog.

Another important thing to remember is this: Most dogs will avoid biting if it is possible, not because they're just everso sweet and cuddly, but because biting, for a dog, is "getting out the big guns." Once they've done it, they've got nothing else in their bag of tricks, and if it doesn't work, they're screwed and they seem to know it. Dogs who have bitten successfully in the past are more prone to bite again. But don't let the number and size of a dog's teeth terrify you to panicking. Your biochemistry changes when you are afraid, (thanks again to the sympathetic nervous system) and dogs can literally see, hear, and smell those changes. If you are freaked out, it is very likely you will communicate your anxiety to the dog without saying a single thing. (That would be bad, anxiety is contagious!) Try to remain as calm as possible. Avoid sudden movements and above all, do NOT offer to punish or strike a dog that is growling at you in a menacing way. The chances are that this particular pooch is either already scared to death of you and simply trying to protect himself, or already looking at you as a source of danger to him, or to his stuff. Carrying on like a lunatic will only intimidate him more, and guess what...that will make him MORE, not less, likely to nail you.

For the record, I have been training dogs for nearly seven years now, and I have been bitten three times. All three bites were obviously my own fault, and only one of them broke the skin. (Unfortunately, it was the skin on my FACE, the little bugger!) Dogs do not bite because they are inherently mean and nasty. Every behavior they exhibit makes absolutely perfect sense to them, and it isn't a dog's fault if we haven't taken the time to understand his motivation. Kindness goes a long way, too. Carry some dog biscuits around with you one day and see how many friends you make!