It's very helpful to familiarize yourself with different breeds before getting involved with one in particular. Then consider visiting a dog pound or shelter. Some of the best dogs I have owned were of the rescued mutt variety. For whatever reason; be it because they had to survive the hand they were dealt, or that they weren't based so much on a specific mutated gene, they have tended to sway towards the more intelligent group. Now before anyone gets upset, every dog and breed I have dealt with has been extremely smart by their own rights, I am just talking in general.

One of the main things you have to take into consideration is your living arrangements. Do you rent, lease, or own your space you live in? Some places have strict rules governing what breeds are and aren't allowed and a lot of insurance companies are now dictating which breeds they will allow on the premises of the home they are underwriting. Be sure to check your policy. Some offer you a chance to sign a waiver for notorious breeds. In my case my Rat terror(terrier) was 10 times more apt to bite someone than my Doberman, yet I had to sign a waiver with my homeowners policy to keep my insurance on my house because of the Doberman's breed reputation. Is it fair, no, but they are the rules.
Another thing to take into consideration is energy level. Contrary to popular belief some of smaller breeds, require far more exercise & play time, than some larger breeds. There again, I said some, not all. You might be inclined to choose a lab puppy to grow up with your children. They are cute as puppies, they make beautiful adult dogs, and they have great reputations. BUT-do you realize they have massive needs as well as your child. The cute little puppies grow into larger puppies, that want lots of attention and when not given it, they tend to crib. That means they chew on EVERYTHING, including your house trim! They are smart, prey driven, and need their minds as well as their bodies exercised quite often! If this does not happen they can become very bored and destructive.
One more tip when trying to learn more about the different breeds is to visit a dog park. Find the breed you are interested in then ask that owner the pro's and con's of owning that particular breed. You can read plenty of books, but it's so much better to see the enthusiasm of the actual owner as they tell you about the good, the bad, and the ugly of that particular breed. If there is no ugly, then seek another owner, that owner is not being honest about their breed. All breeds have some pitfalls. Whether it's hip dysplasia, skin issues, or too much energy. There is always a little something that could be a little different. Doesn't mean we wouldn't trade them for the world, but I would rather be honest to a potential owner so they will be a forever family, than for them to get the animal and return it after it has bonded to them.

Happy hunting and Happy tails from my pack to yours!