Let's say you're out hiking and encounter a stray. Stop and stay still, facing the animal all the while. The key here is face the animal, but do NOT maintain eye contact. Whether the dog is acting aggressively out of fear or out of straight dominance, maintaining direct eye contact is a universal canine sign of a challenge and will do nothing but cause the situation to escalate. Running (or even walking) away may well bring the dog's prey drive into play, and the "chase & bite" instinct will almost assuredly get you bitten if that happens. Talking to the dog in a calm, soothing voice may also help prevent any further advancement.
Sounds silly, but trying to "blow yourself up" to make yourself appear as big and wide as possible will deter a lot of dogs from coming closer. As long as the dog is giving you warnings (growling, eye contact, hackles up, head & ears lowered, etc.), standing your ground and exuding confidence is your best bet. When the dog calms down a bit, slowly start moving away from the area, and never take your eyes away from the dog's position.
If you're actually being charged, charge right back, screaming, yelling, and waving your arms. You'd be surprised at the number of "hard" dogs I've backed off during bitework and testing by doing just this. This may not necessarily send him packing, but in most all cases will at least prevent any further advancement on the dog's behalf.
There is never, and I mean never a reason to throw things at or attempt to injure the dog unless it is obvious that a physical attack is inevitable. As I stated in my post, at this point you do whatever is necessary to end the attack. If that means you must take the animal's life, then so be it. I don't really think I need to get into exact methods here, I'm sure you get the picture. Suffice it to say I carry a 26" ASP baton, First Defense OC spray and my Microtech SOCOM most everywhere I go, but especially when I am out w/my own dogs. As much as I love and respect all forms of life on this planet, I have way too much time (and money) invested in my dogs to allow someone elses irresponsibility to damage them or myself. I do not expect them to protect me from situations that I can handle myself.
It's also important to understand canine body language. Head down, hackles up, tail tucked, are classic signs of fear. This dog will most likely not bite unless he/she is cornered or you do something to trigger that prey drive or the dog is protecting something important to it (such as a litter of puppies) and feels you are too close for comfort. Nonetheless, a fear biter can be dangerous. A dominant dog is another story; head, ears, & tail erect, maintaining unerring eye contact, barking, growling, holding it's ground in a rigid stance. This dog will have no qualms about aggressively charging you, so be aware of that. Also be aware that I have not seen or even heard of one, single dog that would press a fight with a human after being hit with OC spray. If you encounter that many aggressive strays on your outings, there simply is no better defense than OC. In most cases the aggression can be quenched without having to get closer than 6 feet or so. Since any dog bite will do at least some damage to you, this is obviously the best way to go. Considering all the past attacks you've been through, were I you I wouldn't leave home without my OC.
I hope this has been of some help to you, even though I can't help but think that I've left some things out. If you have any future questions or more questions about this subject, feel free to contact me. Take care.
As always,respect,
Tim