I actually keep the ring on the right side of his neck since he's a left hand heeler, so that way I can give the most effective correction. But the prongs are still on the underside of his neck, the most sensitive part.
Mike wears his collar all day every day. When he goes to bed it comes off, but when he wakes up it goes on. This way it's like wearing a shirt, so he doesn't notice it.
I had a foster come in, once, wearing a prong collar that was so big for her it dragged on the ground as she walked! Talk about ill-fitting!!!! They said she was horrible on leash. Come to find she didn't need a prong at all. She went onto a martingale and walked fine on leash after some handler awareness. This is why I firmly believe in only using training collars (prongs, metal chokes, etc) under the instruction of a trainer.
"All changes, even the most longed for, have their melancholy; for what we leave behind us is a part of ourselves; we must die to one life before we can enter another." -Anatole France