Buying a season pass is definitly the best idea.
Options are skiing in Queenstown or Wanaka, most people choose wanaka, its the more chilled ski town and is less touristy.
In wanaka your options are Snowpark, which is just park (as in just park, one chair lift, has a good vibe though), Cardrona, a good all round feild, has pretty good park and some good offpiste, and treble cone which has great steeps and off piste but no park. So depends what your after, lots of people at Otago go for Cardrona, heres the links for them all though
http://http://www.cardrona.com/
http://http://www.treblecone.com/
http://http://www.snowparknz.com/
also join the otago university freestyle sports club when you get there (they have an fb page also) then you'll be in the loop for parties, rides to and accomodation in wanaka.