1.) What breed of dog do I want? It seems a simple question, but it is a good one to ask. Are you a single person who is looking for a pet to keep you company. Do you have a family where there are a lot of people available to help with the dog's care. I wouldn't typically recommend to an owner to get an energetic, young, Labrador if he/she doesn't have the time to walk the dog twice daily for an extended period of time. We will just run into problems with that dog destroying furniture or "misbehaving" because they have so much energy they need to get out. Same thing for a person looking to have a pet to play with, or run with, etc; don't look into getting a Shih Tzu as the pet might not be able to keep up with you. So, ask yourself what breed you might be interested in before getting a pet.
2.) Do I want a puppy versus an adult dog? There are advantages and disadvantages to both young and old dogs. Advantages to young dogs are the ability to help shape their personality, high energy level, and of course overall cuteness; however, you typically have to devote more time, lose sleep, and deal with potty training for these pets. With older dogs you typically get a pet that is already potty trained or may not require as much supervision, but you might not be able to change behavioral issues, might run into medial issues sooner, and the pets life span won't be as long.
4.) Am I mature enough for a pet? Most dogs require constant care and some people may not be ready for a pet. Although they are cute, pets can be a lot of work and you have to be around to care for them. If you are used to going away for weekends or overnight, you need to consider where you might keep your pet if they can't come with you. Some people just don't have time for pets, which is fine, but make sure you realize this before you get your pet.
There are many other questions to ask yourself before looking for a pet. If you don't think you are ready or have other questions, don't hesitate to call your local veterinarian to ask other questions that you may have about pet ownership.