Backpacking and Hiking in New Zealand

A few friends and I have decided on a hiking and backpacking trip to New Zealand. I was wondering what tips and suggestions you all had for me.

(Possibly?) important info Yankee, from Oregon. Used to hiking the Pacific Northwest, in all its mountainous glory.

All of us are mid 20's, in pretty good shape. We all really like beer and lamb.

And i want nothing to do with Aus-OHMYGODANOTHERTHINGISTRYINGTOKILLME-tralia