IMNSHO
Same as all above and more..........
The pet should fit the family. You should consider children, space, exercise and time. Some dog breeds are easy and require little exercise and training and are generally not dominant with family. A great family pet thats fairly easy are labs.
Some dogs require more training and excersice to be a good amimal and I would not recommend these to an uniniated family. Pure breed German shepards and other "working dogs" make great pets but need to be trained properly or you can have problems. This is why people are often scared of greman shepards or pit bulls. Its not the dogs falut that it has been poory, incompitently or incompletely trained but the dog will be punished for it.
Pet stores are generally untrustworthy and staffed by kids. Go to the shelter or a breeder. Muts are generally easier than purebreeds. Browse the web for recommendations on family pets. Read "the monks of new skete"
Personally I have three German Shepards. There fantastic and rewarding dogs but require a lot of training and exercise.
I strongly recommend crate training
Get a puppy under 15 weeks of age preferable 6 to 8 weeks old. read "the monks of new skete"
Do not take your kids to get the dog. You may end up with a poor choice made by kids emotions other than reason. This dog will last 7+ years and an educated choice is important. The kids will love the dog independant of the breed.
katnbat