Britster, I think it depends on what you want to do. If you want to start your own pet boutique, I'd go into a few and ask people how they got started. Hopefully they'll be willing to give away their secrets.
For training, I would google Karen Pryor and clicker training. My bet is that she is at least peripherally involved in a certification program. Cesar Milan probably is as well. You could go to PetCo or some other training place and ask what's needed to get a job there.
There may even be books or wiki "how to" pages on how to start your own business or become a trainer. Maybe for a boutique it would help to start a virtual store front. There are a lot of people here with cottage industries. You could also try to work as a vet's assistant, dog training assistant, job at a boutique, etc.