i graduated from mcgill and skied my ass off during undergrad. Probably a good reason my gpa was what it was... i'd first recommend scrolling through regionals --> Montreal, there's a lot of information in there.
1) Lots of skiing before Christmas. Sauveur, Bromont & Tremblant (to name a few) will be all open. But more importantly, Jay Peak will be open before Christmas - by FAR the best skiing around.
2) If you don't have a buddy who has a car, rent one. Budget on maisoneueve has cheap deals for students.
3) jay used to run a weekend bus (sat + sunday) for crazy cheap, but they dont anymore. worth double checking see if they do
4) you can take the bus from the Berri bus station and ski for the day. the bus leaves real early, 7 or something, but will get you to sauveur by 9 and to Tremblant by 10, coming back the same day. honestly, not really worth it go to all the way to tremblant, but if you're dedicated it's a great way to go to sauveur just for the day. if you want to ski before xmas, and dont have a buddy who is driving, worth looking into
5) if you go to tremblant, by far the cheapest way to stay is in the hostel in town (not the village, in town). worth looking into, makes the trip up there worth it
6) join the ski and snowboard club. i tried a bunch of different ways to ski at mcgill - had a jay season pass, a tremblant season pass, but the SSMU ski and snowboard is the shit. different mtn every week depending on the snow conditions, easy to get on the bus and sleep, you can drink and not have to worry about driving home. and they show dope movies on the bus/cheap drink deals at gerts. i skied a ton of pow last year (relative to snowfall) just because they always choose the best mountains for the week
7) mt royale is great for hitting jumps. my buddies and I would go build/hit a jump during a storm. Actually, most of the time there is a jump already built.
8) there are two mountains within 15 mins of Montreal (but tiny) one St Bruno on the south shore and another in the west island, i'm forgetting the name - i'm sure someone will help me out and tell me. you can take the train to the latter, I never found an easy way to get to bruno without a car
that's sort of everything I learned from being a ski bum at mcgill. Montreal/mcgill is a fucking incredible place to be a skier - there are RIDICULOUS amounts of mountains around the city. just make sure you explore, get up to mt saint anne, up to le massif and hit up all the mountains in northern vt (jay, sugarbush, mad river glen, stowe etc). The snowboard club will give you the chance to hit up all of these overnight.
et voila, c'est tout. bonne chance et bon skier mec