I have just purchased my second Havanese dog, so I can share with you some of what I have learned purchasing these dogs.
I would recommend if you want a show dog, you buy from a breeder with experience showing dogs. That the breeder has been showing dogs for a while and will be willing to be a mentor to you.
If you want a show dog, don't look for best price, look for a quality breeder.
Of course, all health testing of parents of puppy.
Check out the predigree of the puppy, look at the line of dogs the puppy comes from have the breeder tell you about the dogs.
What I really learned the second time around was how important socializing a puppy can be; an experienced good breeder will do this. Where are the puppies kept; in the barn with not much human contact? Or are they with the family getting good quality lovings.
And I question shipping puppies, just from my experience of getting my first puppy, don't really thing it is the best way to start off with your puppy.
And sometimes you have to wait, for a good puppy. I know that is the hardest one!