If you want the right dog you may have to be prepared to travel as the right dog may not be local. I covered various counties and visited many breeders before I chose who I wanted my pup from. Take into consideration that on top of good health you should meet the pups parents or at least the Dam and possibly other family members to see temperament, attitude and possibly drive levels, the breeder (if a good one) will no doubt want to meet you in person before the pup is old enough to take home and you'll choose your Pup or some breeders choose the Pup for you if they know the litter well and your requirements/expectations.
They are a wonderful breed and very natural protectors but they also need time, firm but fair handling, oodles of socialising as pups and good, reward based training and lots of understanding and outlets mentally and physically. You only get out what you put in and I feel I am rewarded daily because of how much work I did with mine as a youngster and do on a daily basis, training is definately an ongoing thing with this breed.
I also feel environment and welfare for the adults is important. Some breeders have big kennels with lots of dogs and I often feel for the dogs because they cannot possibly get that much out of life or the time and attention they deserve - they no doubt get looked after but thats not enough for me personally. Some breeders are smaller, have less dogs but do more with them like show them etc and some breeders have their dogs live in with them. I would want to know that the parents of any pup I was having were sound in most situations outside of their home environment.