Please note that these questions are just guidelines and things that I personally feel are important.  

Bringing in a new family member into your home (and that is exactly what a Boxer puppy is) should be taken very seriously and should never be an impulse purchase.  Purchasing from a registered breeder tends to remove the impulse purchase because most people will have to wait for a puppy.  This is unlike what happens when people walk past a pet store and see a puppy that is JUST TOO CUTE to leave (in my opinion domesticated animals such as dogs and kittens should not be sold in pet stores).  Impulse buying of a puppy is unfortunately very common and never a well thought out decision, this in turn leads to puppies being surrendered or dumped because they have gotten too big, too naughty or are too much work.  Before you make a decade long (at least) commitment to a puppy you need to be sure this is the right decision and one made with an open and objective mind.

Now, what to ask breeders when you are looking to bring a puppy into your family!

Temperament
Temperament should always be high on a breeders list of priorities seeing as most of the puppies from any litter born will be placed in pet homes.  You should always enquire about the temperament of the parents and ancestors especially if you are bringing a puppy into a household with children.

• Are they good with other dogs?  
• Have they been well socialised?  
• Are they good with children? 
  
• What type of interaction with children will be puppy receive before it comes home with us?  

The breeder should be able to answer these questions easily. 

Health
For me the health of our Boxers is a very important part of breeding so I may go on a bit! :D  There are many health issues that affect Boxers, not just one.

• What health tests have the mother and father had?
• Can I see proof of the health tests?
  
• If you haven't tested for other diseases well known in Boxers such as ARVC, can you please tell me why?
  
• Are there any known hereditary diseases with the parents or ancestors?
• If the grandparents have died, what did the mother and father's parents die from?

Any breeder should be able to give you detailed information about your puppies health heritage.

Longevity
When I first started in Boxers the general consensus was that if your Boxer got to 10 years of age then it was great.  I believe that has changed now and we see more and more Boxers hitting the 12 and 13 mark as the norm.

• Given unforeseen events what approximate age do your Boxers to live to?  
• If the grandparents have died then what age did the grandparents die?

If you purchase a puppy from a breeder they should inform you if the mother or father of that puppy dies unexpectedly or at an early age and you should be informed of what caused their death.

Conformation and Construction
For a potential pet puppy buyer the conformation and construction of the puppy shouldn't be the focus, temperament, health and longevity should be.  Conformation and construction are generally things that other breeders hold in high esteem and the breeders themselves will probably keep what they think is the best out of the litter in these traits.