Ahhh Agility, my obsession. Personally I think agility is a great thing not only for the dogs but for you as well...it keeps you both fit and it also helps increase the bond that you have with your dog. I do it with all three of mine, two in competition, and the other is just getting trained.

The best way to get started in agility in my honest opinion is to find a school or training centre in your area that teaches agility that has an experienced trainer. You can try to teach it by yourself but I found that it's always better to get have a pro teach you what to do because they can help you solve any problems that you have or might have in the future.

As for age, you can start them as young as you want just as long you don't do the equipment that would be tough on their bones, like setting the jumps to high. In other words, Kai is old enough to do agility, you just want to make sure that you don't raise the jump heights about 8" or so until the dog is fully grown or 18mnths which is the age that the majority of the agility clubs allow dogs to run in trials.

Hope this helps if you have any more questions, feel free to ask.