Go to the Blue Ice Cafe, drink lots of whatever you drink eat the great food then hop in a chopper do the overland Glacier tour then get out go to the info centre get tickets for a horse ride and do the sunset beach tour. Than stay at the YHA or any of the other great venues. Rafting is also a hit you can fly into the alps get dropped off and do anything from 1-3 day tours.
Avoid the new climbing wall and talk to the locals because they know where to go, make sure you meet a guy called Scumbag aka Greg Brown and you will be the luckiest person in the world.
Also the best things are 30km before hand in HARI HARI because thats where the Wildside backpackers is get the hut out the back and stay with Dan and Kath for as long as you want, suggested minimum is a month.