Accommodations range from deluxe hotels to local inns and motels, with a variety of top-end, luxury lodges, bed-and-breakfasts, farm-stays, backpacker hostels and campgrounds. Because the people are so friendly, we highly recommend that you spend at least a few nights at a bed-and-breakfast or on a local farm. (You'll learn much more about the country by staying with a New Zealand family.)
At Mount Cook, accommodations are scarce except for the Hermitage Lodge (one of the country's most famous hotels) and a youth hostel. If you plan to overnight there, book ahead. The Milford Sound Hotel is closest to the fjords but is generally sold out well in advance. Don't worry if you can't stay there: The nearby town of Te Anau has plenty of options, and it's an easy day trip to Milford Sound from there. For travelers interested in multiday hikes, the Department of Conservation provides several categories of huts along the trails (with varying amenities) for self-sufficient overnight stays. They are occupied first-come, first-served.