I've been working on training my new puppy, Coco, to not bite my hands (which has been rather difficult) and have found that it is important to have something for her to bite on as a substitute for my hand. If I simply grab her nose and tell her not to bite me, but give her nothing afterward, she tries to bite me again (note that this is all playful biting and not 'you look like lunch' biting). She is much better about not biting me when I give her something else to bite on.
There is a spiritual lesson here (actually, this is a general life lesson that applies to everything). If I want to stop a habit, it will be more effective to have something else to replace it with instead of just stopping it and doing nothing more. I struggle a lot with stopping some things and I think one reason why is in some cases I am not replacing them with anything, so I fall back into the old habits rather quickly. I need to find myself a bone or pull toy :).
What about you? Do you have substitutes? Are they effective?
