My prong collar just doesn't look like it's on right, even though it is sitting at the correct spot on his neck. Could you describe how to properly size and put one on?

I've read everything I can on prong collars and am trying to learn the art of using one without doing damage to my dog(s) or myself. My collar never sets down on the dog's neck like it should. It doesn't look right compared to the pictures I see of everyone else's. There seems to be too much space between the neck and the collar (I don't mean loose) but instead something's just not quite right. I have noticed a definite difference between my male Doberman's responsiveness. I don't have to give half dozen corrections on this collar compared to my choke chains but I still know something is wrong. Could you go about describing how to size one properly and to put it on the dog correctly???

Robin