I'm not sure how encouraging this will be, but I've been accepted to the McGill program twice now, so I figured you might want to know what my applications looked like. I don't think you need all this to get in - it's more important that you fit in well with the research agendas of the profs than anything else - but this is what I did:
2002 application: Degree in Ling (4.0 GPA) from a top Canadian school, with one year on exchange at McGill (so I knew some of the profs). I had a couple of (co-authored) conference presentations and published abstracts and 2 years of lab/research assistant work (with national granting council funding in the summers).
2009 application: the above qualifications plus an MA in Ling from a top Canadian school (4.0 GPA) funded by a national granting council. 4 peer-reviewed papers in major publications, one as first author, a bunch of conference presentations, and several years of fieldwork plus teaching at the university level in Canada (language classes) and abroad (linguistics classes). Also, I got in touch with the people I was interested in working with the summer before I applied to remind them that I existed and to sound out the types of research proposals they would support. (This is a very good idea no matter where you are applying!)
Just to note, I think one reason that it's so difficult to get in is that they guarantee a minimum level of funding for all their students for 5 years, so they can only admit as many students as they have the $$ for. The letter I got from them made reference to 'dozens of highly qualified people' and I've noticed that they cap the grad level classes at 10 people on the course listings site so that gives you some idea of acceptance rates. I'd say don't wait around, start reading papers published by McGill faculty and then communicate your enthusiasm for their research to them directly. And honestly, if it were me, I might be okay with taking the qualifying year courses since I can't begin to imagine how difficult the first year would be without that background. Regardless, it is a fantastic place to study, and I wish you the best of luck in your applications.