Your family physician is your gateway to medical treatment. If you're coming down with a cold or if your allergies act up, your family doctor can diagnose you, treat you, and send you on your way with no problems; however, if your condition is proving difficult to pin down or is more complicated than a family doctor is able to deal with, he or she will refer you to a specialist. Here's some more information about specialists and referrals.
It's important to remember that even if you've been watching medical dramas on television for years and you think you know what's wrong with you, you can't go directly to a specialist. Specialists do not take patients who walk in off the street. They only see patients referred to them by another doctor so they can be sure they're not wasting their time on something that could have been handled by a general practitioner; therefore even if it's just a formality sometimes, you need to see your family doctor first.
Once your family doctor has seen you, he or she will get the office assistant to book you an appointment with the appropriate specialist. There won't be a specialist in every discipline at every hospital or even in every town, so if your condition is very rare or serious you might have to travel out of town or even out of province. If your doctor refers you to an out of town specialist, it's important that you go, no matter how big of an inconvenience the traveling is. Your doctor wouldn't have recommended it if it weren't important.
That being said, most specialists will be located close by. Some of the more common specialist doctors you might be sent to see include an otolaryngologist, a cardiologist (a heart doctor), a dermatologist (a doctor who specializes in skin disorders), a surgeon, and a gynecologist (a female reproductive doctor). Your doctor might even refer you to a specialist in dentistry like an endodontist.
The more specialized the discipline, the rarer it is. While your doctor can refer you to a local practitioner of psychiatry for counseling, if you're in need of a neonatal surgeon (someone who operates on newborns), certain types of oncologist (cancer doctors), or pediatricians (children's doctors), you may have to travel.