What do you mean by "look at?"

There is starting them, schooling them, and testing them. I believe the test should be a match, unless you're just going to breed them.

Generally-speaking, 18 months to 2 years is when most knowledgeable dogmen first bump their dogs to get them started. This is when a dog goes from being a puppy to a young adult.
The schooling phase is between 2-3 years of age, which is when the young adult is growing into a fully-mature adult.
The match career should be between 3 to 5 years of age, which is a dog's prime adult years.

I will post my compete article on schooling soon ... but hope this helps in the meantime.

Jack