While riding my bicycle I encountered cats and dogs who were hit by cars, were barely alive, and were obviously beyond saving. They were just laying at the side of the road, and visibly suffering. I have no training or experience in dealing with such a situation. If I can see that the animal is beyond saving, the only thing which keeps me from doing what I believe would be the right thing, is the lack of knowledge. My physical condition is not a problem, I just don't want to cause even more suffering by doing it the wrong way.
How can one save such an animal from suffering in a quick and sure way, without causing extra suffering to it? I'm interested in both the case where I can prepare and have some equipment on me, and the case where I am completely unprepared and empty-handed.