You need a weighted average mark of 75 or above to be considered for marketing honours, plus you also have to complete a set of questions which are used in the selection process. I did a marketing major and got D's for each marketing course (some people think that getting a marketing D isnt very difficult). However, I did three majors rather than the usual two (with those majors being economics, finance and marketing). For these other majors, I was getting mainly D's and the occassional C in 2nd and 3rd year.
Hope that helps,
Matty