The dog you bring home will hopefully be a part of your life for a decade or more. If you have never had a dog, or haven't had one or been around dogs for a long time, you might want to take a little time to be sure you like the reality of dogs before you take the ownership plunge.
If you want a dog for protection, be careful what you choose. For most people, the best protection is a dog that is alert and that will let you know there's someone there so that, if necessary, you can call 911. Large “protection” breeds are not suitable for the average dog owner. Unless you're willing to put in lots of time working with the dog and trainer yourself and learning how to handle him properly, such a dog can be a tremendous liability. A large, forceful dog that you and other family members can't control is much like a loaded gun. In the right hands, it's useful. In the wrong hands, it's dangerous.
One advantage you have as a “researcher” is that dog owners love to talk about their dogs. In fact, you can't shut a lot of us up! So talk to people with dogs—no, wait—don't talk so much, but listen carefully and pay attention. You need to know if the breed you think is oh-so handsome or cute is also a slobberpuss, needs four hours of running exercise a day, is prone to doggy odor, or is otherwise a breed you just won't enjoy.
Talk to serious breeders, to pet owners, and to veterinarians and groomers. Join a discussion list or two on the Internet. There are thousands of dog-oriented websites, discussion lists, and bulletin boards. Some are devoted to dogs in general, others to individual breeds, and still others to training and dog sports, health issues, and just about anything else “doggy” you can imagine. Ask about dogs in general and about the breeds you think you might like in particular. Pay attention!
Consider volunteering a few hours a week for your local shelter. If you zero in on a specific breed but aren't absolutely sure about making the long-term commitment to dog ownership, consider volunteering for a rescue organization for your chosen breed. Most groups are in need of foster homes. They will, of course, screen you and your family to be sure you will be a good temporary harbor for a dog looking for a permanent home. But if you've done your predog homework and think you're ready, chances are they will, too. Be sure you understand the requirements and terms of fostering for that particular organization—get references just as you would for a breeder. If all checks out, you could give needed shelter, love, and attention to a dog in need, and decide for yourself whether dog ownership really is for you. Be forewarned, though—a lot of people fall in love with their foster dogs and wind up adopting them. That's okay—everyone loves a happy ending.
Do some reading as well. Your public library and bookstores should have lots of books on dogs. There are also several excellent magazines devoted to dogs as well as specialized periodicals for most breeds. Read more than one source—several if possible. Sometimes writers make mistakes, and some books are inaccurate, so double-check what you've read. The time and money you invest in learning about dogs before you run out and get one will save you a lot of money and heartache in the long run. You may even decide not to get a dog, or not to get the kind you thought you wanted, and that's okay, too! Better to make such decisions before getting the dog rather than after.
If you get a dog, it should be one that will fit into your life and make both of you happy. Most people can realistically find the right dog in any of several breeds. No single breed of dog is appropriate for every person, or even for the same person at different times in her life.