Most tramping in New Zealand is over 'Conservation Land'. This is public land administered by the Department of Conservation, and includes National Parks, Forest Parks and other reserves. Other Conservation Land may have no reserve status. Access to Conservation Land (with the exception of a few special wildlife sanctuaries) and walking tracks requires neither permission nor payment.
The Department of Conservation is responsible for maintaining huts, campsites, tracks, bridges and other facilities on the Conservation Land. All these facilities are available for public use, although use of some huts and campsites incurs moderate charges. Camping is allowed anywhere unless specifically restricted, for example, camping is only allowed at certain points on the Great Walks, and might not be allowed in city water catchment areas, or sensitive habitats.
New Zealand has an extensive and unparalleled public backcountry hut network. Huts are unlocked and open to all visitors. Payment for most huts is by a hut ticket honesty system. In general, you cannot book hut space.
The Great Walks are a series of popular and high quality tracks over public lands. Camping is restricted, with hut and campsite use paid for with special Great Walks passes. On the busier Great Walks, you book each night's accommodation in a hut or campsite. Other Great Walks simply require the purchase of a pass for a chosen number of nights accommodation, and you may stay at any hut or campsite as you choose
Excerpt courtesy of Matthew Walker - NZ Tramper