You apply on-line to our graduate program (either M.Sc. or Ph.D.). A central admissions committee then reviews the applicants, seeking input from the faculty in relevant research areas. If you indicate on your application that you're interested in a particular research area or areas (or if it's clear from your statement of interest), then the relevant research group(s) will review your application and forward its comments and recommendations to the central committee, who will make the final decision. Thus, directly contacting faculty members (including myself) is unnecessary and will in no way affect your chances of being admitted.
If you have a B.S. degree (or equivalent), then you would normally apply to our M.Sc. program. You're expected to complete your M.Sc. degree in 16-17 months. If you'd like to continue on in the Ph.D. program, then toward the end of your M.Sc. program, you state your intention to continue and there's a review process that determines whether or not you continue on. Note that typically your M.Sc. research represents the early stages of your Ph.D. research. If you have a M.Sc. degree, then you would apply directly to the Ph.D. program.
We are considered the top CS graduate program in Canada and one of the top CS graduate programs in the world. Thus, our graduate program is very competitive (comparable to a top-10 US program) and we're forced to turn away many excellent students.
If you are admitted, you have a funding guarantee of about five years (for either an incoming M.Sc. student that continues on for a Ph.D.) or about four years (for an incoming Ph.D. student with a masters degree). The vast majority of your funding is in the form of a fellowship, giving you maximum time to devote to your research and your courses. In contrast, most US programs will offer you a TA-ship (or, in some cases, an RA-ship), for which you have to work up to 20 hours per week. While you will be offered TA-ships here, they are light (4 hours per week), and are considered small supplements to your main source of fellowship income (each TA-ship boosts your salary by about $2K). In fact, some students choose not to accept them, finding the fellowship to be sufficient income.
Students admitted to our department are free to work with the faculty member of their choosing, providing that person has time to take on another student. While you may be assigned an initial supervisor prior to your arrival based on your stated interests and the supervisory capacity of faculty in that area, you are not bound to that faculty member. When you arrive and meet/interact with our other faculty, you may decide that some other faculty member would make a better supervisor for you for a variety of reasons, including research area or supervisory style. It's important that you converge on a relationship that you're happy with, and we're here to help you find that relationship.
We're always looking for new CL students, and hope that you will consider us among the elite CL/NLP programs that you apply to. Our campus is located in downtown Toronto, the most culturally diverse city in the world. You don't need a car to get around (we have great public transit), and the city has much to offer in the way of music, art, culture, and cuisine. My advice to any keen, prospective graduate student is to talk to our current graduate students (you can track them down on our departmental website) and get their perspective on life as a graduate student here in Toronto.
I wish you the best in your graduate career
(Thanks to my colleagues in the CS department for providing a template for this message.)