If you're working to modify your dog's behavior, always remember this:
1. Immediately reprimand your dog when he does something wrong.
2. Don't drag out the reprimand - keep it to one effective syllable with a strong tone.
3. Pause for 5 seconds to give your dog a chance to behave. Remember that behaving can simply be NOT doing something. Although it looks like nothing to you, it's actually a behavior for your dog - calm, relaxed patient waiting.
4. PRAISE YOUR DOG!!!! Make it a party when he comes to you, say "Thank you" in an upbeat tone when she drops garbage she found on the sidewalk...get excited!
5. Reward your dog after EVERY step of the learning process. In other words, when you ask your dog to come and he does, praise him BEFORE you ask him to sit and then praise him again when he sits. Don't string a list of commands together and only praise your dog when the grocery list is complete. If you do, he'll only feel rewarded for the last item on the list.
I know it's easy to get overwhelmed when you're trying to stop your dog from displaying a behavior, but NEVER forget that once he does stop displaying the bad behavior he's actually displaying a good behavior and deserves his due praise.
Positive, fun, exciting lessons make your dog WANT to please you.