Remember that training is an ongoing process. You will never be completely finished. It is important to keep working on obedience training throughout the life of your dog. People who learn a language at a young age but stop speaking that language may forget much of it as they grow older. The same goes for your dog: use it or lose it. Running through even the most basic tricks and commands will help them stay fresh in your dog's mind. Plus, it's a great way to spend time with your dog.
Even if your pup gets the best start in life, he will still likely develop some “problem” behaviors as he grows up. We put the word “problem” in quotes because most of these behaviors are natural and normal dog behaviors, but they are not welcome in the human world. Behaviors like jumping on you as a gesture of affection, nipping at your hands as an invitation to play, and sniffing you in inappropriate places are all perfectly acceptable behaviors for dogs to do to other dogs.
According to the USDAA, there are over 150 breeds of dogs, including mixed-breed dogs, involved in agility. Some breeds, like the Australian Shepherd and the Dutch Shepherd, are known for excelling at the sport. However, you should not let the fact that you have a Golden Retriever or a mixed-breed dog stop you from trying it. If your dog is playful and energetic, it will probably enjoy agility training.
Martingale collars (also called limited-slip collars) are usually made of flat nylon with a smaller fixed-length section (made of either nylon or a short length of chain) that, when pulled on by the leash, shortens up tightening the collar around the dog's neck, to a limited extent. When properly fitted, martingales are looser than flat-buckle collars when not tightened, and less severely corrective than slip collars when tightened.