What I forgot to mention is that if you're standing there petrified, there is a greater chance the dog will become aggressive. There's not much that can be done about that if you're scared of dogs, except perhaps some experience of dogs.

It's one of those things you get better at the more you do of it.

http://en.wikipedia.org/wiki/List_of_fatal_dog_attacks_in_the_United_States
This link tells of 327 dog related[killed by]deaths in the USA, over 20 years.
While pit bulls are seen to be worse other breeds kill too.
Here,just in NSW such deaths may well be more per head of population.
Is mise that info is the best but not fool proof.
If a big dog is involved you are fighting for your very life inflicting great pain on it may well not be enough.
Watch one tearing in to a pig still after being gored, go hard eyes throat .
Try to shout not scream panic fires them.
But we should not have to share our streets or our yards with them ever.
It takes years for local government and state, federal too, to do what should take a day.
How many more deaths? you tell me.
In the right hands the right yard ok but who knows who owns one

To answer my own question.
If a dog attacks you, for whatever reason, throw your weak arm (the one that's going to be bitten), across your body with the elbow at right angles and with the lower arm as far forward as your physique allows.
Look the dog in the eyes over your arm.
Most times the dog will fasten onto the extended arm (that's why you advance your weak arm).
Encircle the dog's neck with your strong arm and break its neck.
If the breed has a strong neck then it may be necessary to fall onto your weak arm and add your body's weight to the leverage.

Another method is to grasp the dog's legs when it leaps and pull the legs apart, this either breaks its legs or fractures the rib cage; either way it's out of action; however this method leaves one open to bites.

Preferable is to stab it when it leaps.
The weak arm can be used as gripping the arm leaves the dog open to a disembowelling cut.

A pistol would be best of all especially where there is more than one dog.

The humble walking stick is handy as well.
If the dog can be induced to attack the end of the stick then a strong thrust via the throat will kill it or render it unfit to continue.

However if you feel threatened by dogs don't carry ANYTHING with the intention of protecting yourself as that is illegal.

I should actually point out that I myself have actually been mauled by a dog when I was a child- and of all breeds, by a blue heeler.

In contrast to all of the family pitbulls, bull terriers, great danes, rottweilers, german shepherds, and dobermans I've encountered have jumped on me to lick my face, were a much safer experience.
Even when confronted by other aggressive dogs, they generally ignored them outright unless they were actually bitten by the other dogs.

The only other dog I know that ever attacked a child was a larger breed of a Japanese hunting dog- unlike its sibling who made no attempt and was incredibly passive.

It seems very much that the 'dangerous breed' issue is nothing but an excuse for bad owners to point the finger away from themselves; wanting to minimize threats to public safety EXCEPT when their own preferred breeds come under the spotlight (or of course, the fear that if their own aggressive animal goes to attack another dog, the other dog might actually pose a threat when trying to protect itself).

I might add that a dog's mouth is very vunerable; pressure on its tongue and lower jaw will stop it from biting.
However the thumb or fingers may be severed if one is not very, very fast.

If in a fight with a dog, and that's what it should be if one is attacked, then gripping the lower jaw and the upper and pulling them apart will dislocate the lower jaw and render the dog defenceless.

All good advice, Is Mise, but the best thing is to simply not get the thing going. If you have got it going, make whatever you do count as much as you can, because the dog will surely be deadly serious once it starts.

As I said earlier, dogs don't simply attack with no reason. If people aren't used to dogs they can provoke them into an attack completely unwittingly, making it appear to them to be unprovoked.

That was my point in regard to education.