In my mind, and reading all the replies posted here, it really all boils down to one thing - what motivation does the 'breeder' have for producing the litter? Those who are breeding for show will be focussing on producing dogs which fit the standard as closely as possible and are probably hoping to have something good enough from the litter to keep themselves for the future. Breeders producing dogs for performance may be less concerned about producing dogs which match the standard (but they should still be aiming to adhere pretty closely to breed type) but will be focussing on producing top notch competition dogs. Again, they will be hoping to keep one for themselves. Some breeders don't show or compete in performance events but aim to produce nice pets. This is where you do have to be more careful though. If their motivation is to produce a pup to keep, then chances are they are going to invest time, effort and knowledge into producing well bred puppies. However, if this is the case they are unlikely to breed often as they will only have one or two pet bitches. The difficulty here seems to be that people frequently start with the best intentions, breeding a litter from a much loved pet, maybe to give her a companion. If things go well (and weirdly they usually do for first timers!) they suddenly realise that perhaps this might be a way of making a little bit extra. They breed another litter, but this time, with the idea of making a profit, they use a poorer quality/cheaper dog, perhaps cut corners when rearing the litter. Before too long they are breeding a couple or more litters a year, purely to sell and make money from. These are not large scale puppy millers with really poor conditions, but they still are not a good bet because all the investment that 'competition' breeders put into raising a quality litter will have been skimped on. I'm sure there are very good breeders who do breed annually from one or two pet dogs for the pet market and who do everything right, but it might not be that easy to spot which ones they are.
If a breeder genuinely puts the welfare of their dogs/puppies before anything else, they will not be keen to sell a puppy! They will not let their precious babies go to anyone without finding out quite a lot about every potential purchaser's lifestyle. Be wary of any breeder who dosn't want to know about where you live, your lifestyle, family etc. Don't volunteer all the information up front without being asked, let the breeder ask you some questions too. If they act like a salesperson in a store, then red flags should be waving as all they are interested in is making a sale, not ensuring that you and the puppy are good matches for each other.
Best of luck, it is more than worth all the effort to end up with a healthy, well adjusted pup that you can enjoy for hopefully the next 15 years or more.