Do you live a quiet, solitary life in the country with few visitors? The breeds that are "one-person" dogs would be a choice for you.
Does someone in your family have allergies? The hypo-allergetic breeds can solve the problem.
Do you have a high-traffic household, people in and out of all ages, are active and expect a dog to share this outlook? Research breeds that are bred to be congenial under most all circumstances and accept strangers without natural suspicion.
Is your family one that wants a dog that shares your life, yet will watch over family and domicile? Is willing to accept a few strangers and outside family, but would need some time to bring in more people on a regular basis?
Are you very active, bike, hike, run, would like to compete in dog sports, enjoy groups of people and dogs - dog parks and events? Research your breed of choice and be realistic with what that breed needs.
Most dogs that end up in shelters or moved from home to home were impulse adoptions or purchases which "didn't fit" a household - the dog is the one that suffers - take the time to find your next forever friend. It will be worth it. Feel free to contact me and we can discuss your needs and the best possible choices for you to look into.