Get onto the National Geographic Channel and find this series. His name is Caesar Millan. This guy is NOT a whacko... he corrects negative dog behaviors using dog psychology. He runs a dog rescue center, or something like that in/around LA. Has a PACK of 30+ dogs that live together in one big 'yard'; pits, dobermans, rotts, gsd, poodles, etc. etc. and these dogs were all given-up because of problem behaviors. I'm talking this guy pulls-off miracles. From aggression to pulling while walking... this guy will have an answer to your concerns... just watch a few episodes, as he 'solves' any conceivable problem behavior... and tells the people how to do it themselves. HIGHLY RECOMMEND!!!