I hear this all the time. My first question to anyone who asks me this question is, do you and your dog know what whoa means? Most people say yes, but in fact, they don't. Whoa means only one thing.... DON'T MOVE YOUR FEET. That's it, nothing else. And the word whoa shouldn't be used for anything else. They can move their head, eyes, tail, but not the feet. Now that you know what whoa really means, you can now teach it to your dog. The next step is to make sure your dog whoa's every time you say the word. This is where the training comes in. You have to be presistant about it and enforce it every time you say the word. If they work well at whoa at home, take them somewhere else and work your whoa drills. Most of the time, they will break in new surroundings, or with another dog present. Work with plenty of distractions, and before long when you say whoa, your dog will stick his feet to the ground and not move a muscle!