I am a positive reinforcement - clicker trainer in RI. I would also suggest a few things additionally to the advice given. Establish a potty area, that you go to each and every time on leash. be totally boring, just stand there. As your pup starts to eliminate, introduce a verbal cue (I use "hurry up"), and as your pup is finishing use a reward marker - clicker or the word "yes" and give a treat. After eliminating, play with your pup outside if that is reinforcing, or if raining go inside for a little playtime. This is so dog does not learn on he eliminates fun is over. Putting elimination on cue, makes rainy cold days easier, and reinforcing with a treat builds the desired behavior. Remember that pups typically need to eliminate 20 minutes after eating, upon waking, after chewing on something, or playing.
Good luck, Beth
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