Hi there,
The best place to search for the breeder of your next family member is your local boxer club. The worst place to find a puppy is a pet store or through the newspaper.
Miami Valley Boxer Club is who you want to get into touch with.
Make sure that the prospective parents of your puppy are health tested for heart, hip and thyriod problems, and make sure that the breeder shows their dogs in Conformation to ensure that your boxer baby will look like a boxer when he or she is grown. Visit the breeders home prior to picking up your puppy to ensure that they are cared for in a proper manner. Ask pointed questions about temperament issues like aggression, shyness or fearfulness, separation anxiety, etc. Make sure that the breeder does their part to keep our shelters from becoming overfull by asking if they will take the dog back at any time should you no longer be able to care for it. Expect to spay or neuter your puppy if interested in a pet quality puppy, or expect to show an health test your puppy when it becomes an adult if interested in a breed quality puppy.
Last but not least, have you considered rescue?
Lighthouse Boxer Rescue has many adoptable dogs coming through their program on a fairly regular basis. The advantages of adopting an older dog are to numerous to list, but include: no potty training hastle, the dogs are up to date on vaccinations, spayed or neutered, cheaper than buying a puppy, and most come with some obedience training.
Good luck in finding your next family member. Remember, this is a decision that should not be rushed and can last throughout the next 10-14 years of your life!
I hope this helps!