The best way to find a good collie breeder is to use the American Kennel Club's Breeder Referral page. You can also contact local breed organizations or all-breed kennel clubs for referrals.
Your local collie breed club may be a good starting point, because finding a breeder in your general area can help with the purchase process. It can be a good idea to contact several breeders at first, especially if you want a collie for a specific purpose. For example, some collie breeders may focus more on show lines, while others focus more on working ability.
When locate a few breeders you may want to work with, reach out to them and ask to visit their property if possible. Good breeders should be happy to have you visit and their dogs should be in good condition. Be wary of breeders that produce many litters every year, as well as breeders who sell their puppies to pet stores. A good breeder should interview you to make sure you can provide a good home for the puppy.
Be sure to ask any potential breeder about health testing. Collie breeders need to perform certain health tests on parents and puppies, especially checking the eyes for a condition called collie eye anomaly, Good collie breeders should be upfront and knowledgeable about this genetic condition.