What most naturally follows?

How to train your service dog without a professional trainer
Find a dog that is the right age.
It can be difficult to know if a puppy under the age of 6 months has the right blend of intelligence and attention to make a good service dog. Charity's that train up service dogs, have a high' drop out' rate, even when they have used their knowledge to select likely candidates.
Buying a puppy with the express purpose of it becoming a service dog is a gamble. It might be better to source a young dog which has been properly trained and has established their personality already.